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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1706.00693
|
David Crouse
|
David Crouse, Joseph Skufca
|
Relativistic Time Dilation and Length Contraction in Discrete Space-Time
using a Modified Distance Formula
|
This paper is duplicated in a much more thorough paper of ours (paper
ID# arXiv:1803.03126) on arxiv. Again, please see paper arXiv:1803.03126
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work, the relativistic phenomena of Lorentz contraction and time
dilation are derived using a modified distance formula appropriate for discrete
space. This new distance formula is different than Pythagoras's theorem but
converges to it for distances large relative to the Planck length. First, four
candidate formulas developed by different people over the last 70 years will be
considered. Three of the formulas are shown to be identical for conditions that
best describe discrete space; this equation is then used in the rest of the
paper. It is shown that this new distance formula is applicable to all
size-scales, from the Planck length upwards, and solves two major historical
problems associated with a discrete space-time model. One problem it solves is
maintaining isotropy in discrete space. The second problem it solves is the
commonly perceived incompatibility of the model's concept of an immutable
"atom" of space and the Lorentz contraction of this atom required by special
relativity. With the new distance formula, it is shown that the Lorentz
contraction of the atom of space does not occur regardless of the relative
velocities of two reference frames. It is also shown that time dilation of the
atom of time does not occur. Also discussed is the possibility of any object
being able to travel at the speed of light for specific temporal durations
derived in this work.
|
[
{
"created": "Thu, 1 Jun 2017 16:29:09 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Oct 2018 16:24:04 GMT",
"version": "v2"
}
] |
2018-10-10
|
[
[
"Crouse",
"David",
""
],
[
"Skufca",
"Joseph",
""
]
] |
In this work, the relativistic phenomena of Lorentz contraction and time dilation are derived using a modified distance formula appropriate for discrete space. This new distance formula is different than Pythagoras's theorem but converges to it for distances large relative to the Planck length. First, four candidate formulas developed by different people over the last 70 years will be considered. Three of the formulas are shown to be identical for conditions that best describe discrete space; this equation is then used in the rest of the paper. It is shown that this new distance formula is applicable to all size-scales, from the Planck length upwards, and solves two major historical problems associated with a discrete space-time model. One problem it solves is maintaining isotropy in discrete space. The second problem it solves is the commonly perceived incompatibility of the model's concept of an immutable "atom" of space and the Lorentz contraction of this atom required by special relativity. With the new distance formula, it is shown that the Lorentz contraction of the atom of space does not occur regardless of the relative velocities of two reference frames. It is also shown that time dilation of the atom of time does not occur. Also discussed is the possibility of any object being able to travel at the speed of light for specific temporal durations derived in this work.
|
1909.01275
|
Shuxuan Ying
|
Peng Wang, Haitang Yang, Shuxuan Ying
|
Thermodynamics and Phase Transition of a Gauss-Bonnet Black Hole in a
Cavity
|
15 pages, 12 figures
|
Phys. Rev. D 101, 064045 (2020)
|
10.1103/PhysRevD.101.064045
|
CTP-SCU/2019017
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Considering a canonical ensemble, in which the temperature and the charge on
a wall of the cavity are fixed, we investigate the thermodynamics of a
D-dimensional Gauss-Bonnet black hole in a finite spherical cavity. Moreover,
it shows that the first law of thermodynamics is still satisfied. We then
discuss the phase structure and transition in both five and six dimensions.
Specifically, we show that there always exist two regions in the parameter
space. In one region, the system possesses one single phase. However in the
other region, there could coexist three phases and a van der Waals-like phase
transition occurs. Finally, we find that there is a fairly close resemblance in
thermodynamic properties and phase structure of a Gauss-Bonnet-Maxwell black
hole, either in a cavity or in anti-de Sitter space.
|
[
{
"created": "Tue, 3 Sep 2019 16:14:23 GMT",
"version": "v1"
},
{
"created": "Sun, 8 Sep 2019 17:30:27 GMT",
"version": "v2"
}
] |
2020-03-25
|
[
[
"Wang",
"Peng",
""
],
[
"Yang",
"Haitang",
""
],
[
"Ying",
"Shuxuan",
""
]
] |
Considering a canonical ensemble, in which the temperature and the charge on a wall of the cavity are fixed, we investigate the thermodynamics of a D-dimensional Gauss-Bonnet black hole in a finite spherical cavity. Moreover, it shows that the first law of thermodynamics is still satisfied. We then discuss the phase structure and transition in both five and six dimensions. Specifically, we show that there always exist two regions in the parameter space. In one region, the system possesses one single phase. However in the other region, there could coexist three phases and a van der Waals-like phase transition occurs. Finally, we find that there is a fairly close resemblance in thermodynamic properties and phase structure of a Gauss-Bonnet-Maxwell black hole, either in a cavity or in anti-de Sitter space.
|
1911.05793
|
Thiago Pereira
|
Mikjel Thorsrud, Ben D. Normann, Thiago S. Pereira
|
Extended FLRW Models: dynamical cancellation of cosmological
anisotropies
|
31 pages, 2 figures; v2: minor amendments to match the version
published in CQG
|
Class. Quantum Grav. 37 (2020) 065015
|
10.1088/1361-6382/ab6f7f
| null |
gr-qc astro-ph.CO hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We investigate a corner of the Bianchi models that has not received much
attention: "extended FLRW models" (eFLRW) defined as a cosmological model with
underlying anisotropic Bianchi geometry that nevertheless expands isotropically
and can be mapped onto a reference FLRW model with the same expansion history.
In order to investigate the stability and naturalness of such models in a
dynamical systems context, we consider spatially homogeneous models that
contain a massless scalar field $\varphi$ and a non-tilted perfect fluid
obeying an equation of state $p=w\rho$. Remarkably, we find that matter
anisotropies and geometrical anisotropies tend to cancel out dynamically.
Hence, the expansion is asymptotically isotropic under rather general
conditions. Although extended FLRW models require a special matter sector with
anisotropies that are 'fine-tuned" relative to geometrical anisotropies, our
analysis shows that such solutions are dynamically preferred attractors in
general relativity. Specifically, we prove that all locally rotationally
symmetric Bianchi type III universes with space-like $\nabla_\mu\varphi$ are
asymptotically shear-free, for all $w\in[-1,1]$. Moreover, all shear-free
equilibrium sets with anisotropic spatial curvature are proved to be stable
with respect to all homogeneous perturbations for $w\geq -1/3$.
|
[
{
"created": "Wed, 13 Nov 2019 20:06:48 GMT",
"version": "v1"
},
{
"created": "Thu, 20 Feb 2020 18:15:50 GMT",
"version": "v2"
}
] |
2020-02-21
|
[
[
"Thorsrud",
"Mikjel",
""
],
[
"Normann",
"Ben D.",
""
],
[
"Pereira",
"Thiago S.",
""
]
] |
We investigate a corner of the Bianchi models that has not received much attention: "extended FLRW models" (eFLRW) defined as a cosmological model with underlying anisotropic Bianchi geometry that nevertheless expands isotropically and can be mapped onto a reference FLRW model with the same expansion history. In order to investigate the stability and naturalness of such models in a dynamical systems context, we consider spatially homogeneous models that contain a massless scalar field $\varphi$ and a non-tilted perfect fluid obeying an equation of state $p=w\rho$. Remarkably, we find that matter anisotropies and geometrical anisotropies tend to cancel out dynamically. Hence, the expansion is asymptotically isotropic under rather general conditions. Although extended FLRW models require a special matter sector with anisotropies that are 'fine-tuned" relative to geometrical anisotropies, our analysis shows that such solutions are dynamically preferred attractors in general relativity. Specifically, we prove that all locally rotationally symmetric Bianchi type III universes with space-like $\nabla_\mu\varphi$ are asymptotically shear-free, for all $w\in[-1,1]$. Moreover, all shear-free equilibrium sets with anisotropic spatial curvature are proved to be stable with respect to all homogeneous perturbations for $w\geq -1/3$.
|
gr-qc/0610144
|
David Kubiznak
|
David Kubiznak, Valeri P. Frolov
|
Hidden Symmetry of Higher Dimensional Kerr-NUT-AdS Spacetimes
|
4 pages, some discussion and references are added
|
Class.Quant.Grav.24:F1-F6,2007
|
10.1088/0264-9381/24/3/F01
|
Alberta-Thy-10-06
|
gr-qc hep-th
| null |
It is well known that 4-dimensional Kerr-NUT-AdS spacetime possesses the
hidden symmetry associated with the Killing-Yano tensor. This tensor is
"universal" in the sense that there exist coordinates where it does not depend
on any of the free parameters of the metric. Recently the general higher
dimensional Kerr-NUT-AdS solutions of the Einstein equations were obtained. We
demonstrate that all these metrics with arbitrary rotation and NUT parameters
admit a universal Killing-Yano tensor. We give an explicit presentation of the
Killing-Yano and Killing tensors and briefly discuss their properties.
|
[
{
"created": "Sat, 28 Oct 2006 06:56:49 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Dec 2006 06:02:38 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Kubiznak",
"David",
""
],
[
"Frolov",
"Valeri P.",
""
]
] |
It is well known that 4-dimensional Kerr-NUT-AdS spacetime possesses the hidden symmetry associated with the Killing-Yano tensor. This tensor is "universal" in the sense that there exist coordinates where it does not depend on any of the free parameters of the metric. Recently the general higher dimensional Kerr-NUT-AdS solutions of the Einstein equations were obtained. We demonstrate that all these metrics with arbitrary rotation and NUT parameters admit a universal Killing-Yano tensor. We give an explicit presentation of the Killing-Yano and Killing tensors and briefly discuss their properties.
|
2110.15643
|
Vegard Undheim Mr.
|
Vegard Undheim
|
First post-Newtonian correction to gravitational waves produced by
compact binaries: How to compute relativistic corrections to gravitational
waves using Feynman diagrams
|
Master's thesis, 101 pages. Supervised by Alex B. Nielsen and Jens O.
Andersen
| null | null | null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
The purpose of this thesis is to calculate the relativistic correction to the
gravitational waves produced by compact binaries in the inspiral phase. The
correction is up to the next to leading order, the so-called first
post-Newtonian order (1PN), which are correctional terms proportional to
$(v/c)^2$ compared to leading order, Newtonian, terms. These corrections are
well known in the literature, even going beyond the first order corrections, so
why is it computed again here? In later years, an alternative approach for
computing these terms using effective field theory has emerged. This thesis
investigates this approach by replicating it, and attempts to make this
approach more accessible to those not familiar with effective field theories.
It has been claimed that this approach greatly simplifies the complicated
calculations of gravitational waveforms, and even provides the required
intuition for 'physical understanding'. By this master student that was found
not to be entirely correct. The calculations were made easier for those with a
rich background in quantum field theory, but for those who are not well
acquainted with quantum field theory this was not the case. It was, however,
found to be a worthwhile method as a means for deepening one's understanding of
gravity, and might provide a shorter route for some alternative theories of
gravity to testable predictions.
|
[
{
"created": "Fri, 29 Oct 2021 09:33:32 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Sep 2022 08:27:41 GMT",
"version": "v2"
}
] |
2022-09-26
|
[
[
"Undheim",
"Vegard",
""
]
] |
The purpose of this thesis is to calculate the relativistic correction to the gravitational waves produced by compact binaries in the inspiral phase. The correction is up to the next to leading order, the so-called first post-Newtonian order (1PN), which are correctional terms proportional to $(v/c)^2$ compared to leading order, Newtonian, terms. These corrections are well known in the literature, even going beyond the first order corrections, so why is it computed again here? In later years, an alternative approach for computing these terms using effective field theory has emerged. This thesis investigates this approach by replicating it, and attempts to make this approach more accessible to those not familiar with effective field theories. It has been claimed that this approach greatly simplifies the complicated calculations of gravitational waveforms, and even provides the required intuition for 'physical understanding'. By this master student that was found not to be entirely correct. The calculations were made easier for those with a rich background in quantum field theory, but for those who are not well acquainted with quantum field theory this was not the case. It was, however, found to be a worthwhile method as a means for deepening one's understanding of gravity, and might provide a shorter route for some alternative theories of gravity to testable predictions.
|
2405.01297
|
Cyril Pitrou
|
Giulia Cusin, Cyril Pitrou, Camille Bonvin, Aur\'elien Barrau, Killian
Martineau
|
Boosting gravitational waves: a review of kinematic effects on
amplitude, polarization, frequency and energy density
|
38 pages, 5 figures
| null | null | null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We review the kinematic effects on a gravitational wave due to either a
peculiar motion of the astrophysical source emitting it or a local motion of
the observer. We show, at fully non-linear order in velocity, that the
amplitude of the wave is amplified by the Doppler factor in the case in which
the source moves with respect to a reference frame, while it is invariant if
the observer moves (with respect to a reference observer). However, the
observed specific intensity transforms in the same way under a boost of the
source or of the observer. We also show at fully non-linear order that under a
boost (of either source or observer), the polarization tensor is rotated in the
same way the wave direction is rotated by aberration, such that the only net
effect of a boost on polarization is to change the phase of the helicity
components. We apply these results to a wave emitted by a binary system of
compact objects in the cosmological context.
|
[
{
"created": "Thu, 2 May 2024 14:00:00 GMT",
"version": "v1"
}
] |
2024-05-06
|
[
[
"Cusin",
"Giulia",
""
],
[
"Pitrou",
"Cyril",
""
],
[
"Bonvin",
"Camille",
""
],
[
"Barrau",
"Aurélien",
""
],
[
"Martineau",
"Killian",
""
]
] |
We review the kinematic effects on a gravitational wave due to either a peculiar motion of the astrophysical source emitting it or a local motion of the observer. We show, at fully non-linear order in velocity, that the amplitude of the wave is amplified by the Doppler factor in the case in which the source moves with respect to a reference frame, while it is invariant if the observer moves (with respect to a reference observer). However, the observed specific intensity transforms in the same way under a boost of the source or of the observer. We also show at fully non-linear order that under a boost (of either source or observer), the polarization tensor is rotated in the same way the wave direction is rotated by aberration, such that the only net effect of a boost on polarization is to change the phase of the helicity components. We apply these results to a wave emitted by a binary system of compact objects in the cosmological context.
|
2309.12478
|
Shahram Jalalzadeh
|
P. F. da Silva Junior, E. W. de Oliveira Costa, and S. Jalalzadeh
|
Emergence of fractal cosmic space from fractional quantum gravity
|
20 pages, 1 figure, to appear in Eur. Phys. J. Plus
|
Eur. Phys. J. Plus 138, 862 (2023)
|
10.1140/epjp/s13360-023-04506-z
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
Based on Padmanabhan's theory, the spatial expansion of the Universe can be
explained by the emergence of space as cosmic time progresses. To further
explore this idea, we have developed fractional-fractal Friedmann and
Raychaudhuri equations for an isotropic and homogeneous universe. Our analysis
has also delved into how Padmanabhan's concept fits into the framework of
fractional quantum gravity. Our research shows that a fractal horizon model
strongly supports the validity of the emerging Universe paradigm and its
connection to horizon thermodynamics. This study indicates early how the
emergent gravity perspective might manifest in quantum gravity. By utilizing
the fractional-fractal Friedmann and Raychaudhuri equations, we have
established that the mainstream cosmology model can be justified without a dark
matter component. As a result, the standard $\Lambda$CDM model has been reduced
to $\Lambda$-Cold Baryonic Matter, which has significant implications for our
understanding of the Universe.
|
[
{
"created": "Thu, 21 Sep 2023 20:49:56 GMT",
"version": "v1"
}
] |
2023-09-29
|
[
[
"Junior",
"P. F. da Silva",
""
],
[
"Costa",
"E. W. de Oliveira",
""
],
[
"Jalalzadeh",
"S.",
""
]
] |
Based on Padmanabhan's theory, the spatial expansion of the Universe can be explained by the emergence of space as cosmic time progresses. To further explore this idea, we have developed fractional-fractal Friedmann and Raychaudhuri equations for an isotropic and homogeneous universe. Our analysis has also delved into how Padmanabhan's concept fits into the framework of fractional quantum gravity. Our research shows that a fractal horizon model strongly supports the validity of the emerging Universe paradigm and its connection to horizon thermodynamics. This study indicates early how the emergent gravity perspective might manifest in quantum gravity. By utilizing the fractional-fractal Friedmann and Raychaudhuri equations, we have established that the mainstream cosmology model can be justified without a dark matter component. As a result, the standard $\Lambda$CDM model has been reduced to $\Lambda$-Cold Baryonic Matter, which has significant implications for our understanding of the Universe.
|
gr-qc/9801088
|
Masayuki Tanimoto
|
Masayuki Tanimoto
|
New varieties of Gowdy spacetimes
|
13 pages with no figure. A reference added, and typos corrected. To
appear in J.Math.Phys
|
J.Math.Phys. 39 (1998) 4891-4898
|
10.1063/1.532497
| null |
gr-qc
| null |
Gowdy spacetimes are generalized to admit two commuting spatial "local"
Killing vectors, and some new varieties of them are presented, which are all
closely related to Thurston's geometries. Explicit spatial compactifications,
as well as the boundary conditions for the metrics are given in a systematic
way. A short comment on an implication to their dynamics toward the initial
singularity is made.
|
[
{
"created": "Tue, 27 Jan 1998 11:27:23 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Jun 1998 00:12:29 GMT",
"version": "v2"
}
] |
2015-06-25
|
[
[
"Tanimoto",
"Masayuki",
""
]
] |
Gowdy spacetimes are generalized to admit two commuting spatial "local" Killing vectors, and some new varieties of them are presented, which are all closely related to Thurston's geometries. Explicit spatial compactifications, as well as the boundary conditions for the metrics are given in a systematic way. A short comment on an implication to their dynamics toward the initial singularity is made.
|
1710.11294
|
Nishanth Abu Gudapati
|
Nishanth Gudapati
|
A Positive-Definite Energy Functional for Axially Symmetric Maxwell's
Equations on Kerr-de Sitter Black Hole Spacetimes
|
Journal version
|
C. R. Math. Rep. Acad. Sci. Canada Vol. 40 (2) 2018, pp. 39-54
| null | null |
gr-qc math.AP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We prove that there exists a phase space of canonical variables for the
initial value problem for axially symmetric Maxwell fields propagating in
Kerr-de Sitter black hole spacetimes such that their motion is restricted to
the level sets of a positive-definite Hamiltonian, despite the ergo-region.
|
[
{
"created": "Tue, 31 Oct 2017 01:52:24 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Jul 2018 17:21:41 GMT",
"version": "v2"
}
] |
2018-07-23
|
[
[
"Gudapati",
"Nishanth",
""
]
] |
We prove that there exists a phase space of canonical variables for the initial value problem for axially symmetric Maxwell fields propagating in Kerr-de Sitter black hole spacetimes such that their motion is restricted to the level sets of a positive-definite Hamiltonian, despite the ergo-region.
|
1806.00742
|
Richard Woodard
|
S. P. Miao (NCKU), T. Prokopec (Utrecht) and R. P. Woodard (Florida)
|
The Graviton Tail almost Completely Wags the Dog
|
17 pages, 1 figure, uses LaTeX2e
|
Phys. Rev. D 98, 025022 (2018)
|
10.1103/PhysRevD.98.025022
|
UFIFT-QG-18-02
|
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
One graviton loop corrections to the vacuum polarization on de Sitter show
two interesting infrared effects: a secular enhancement of the photon electric
field strength and a long range running of the Coulomb potential. We show that
the first effect derives solely from the "tail" term of the graviton
propagator, but that the second effect does not. Our result agrees with the
earlier observation that the secular enhancement of massless fermion mode
functions derives from solely from the tail term. We discuss the implications
this has for the important project of generalizing to quantum gravity the
Starobinsky technique for summing the series of leading infrared effects from
inflationary quantum field theory.
|
[
{
"created": "Sun, 3 Jun 2018 06:48:02 GMT",
"version": "v1"
}
] |
2018-08-01
|
[
[
"Miao",
"S. P.",
"",
"NCKU"
],
[
"Prokopec",
"T.",
"",
"Utrecht"
],
[
"Woodard",
"R. P.",
"",
"Florida"
]
] |
One graviton loop corrections to the vacuum polarization on de Sitter show two interesting infrared effects: a secular enhancement of the photon electric field strength and a long range running of the Coulomb potential. We show that the first effect derives solely from the "tail" term of the graviton propagator, but that the second effect does not. Our result agrees with the earlier observation that the secular enhancement of massless fermion mode functions derives from solely from the tail term. We discuss the implications this has for the important project of generalizing to quantum gravity the Starobinsky technique for summing the series of leading infrared effects from inflationary quantum field theory.
|
gr-qc/9907078
|
Moshe Carmeli
|
Moshe Carmeli (Ben Gurion U.) and Shimon Malin (Colgate U.)
|
SL(2,C) Gauge Theory of Gravitation and the Quantization of the
Gravitational Field
|
6 pages, published in Intern. j. Theor. Phys. Vol. 37, No. 10,
pp.2615-2620 (1998)
|
Int.J.Theor.Phys. 37 (1998) 2615-2620
| null | null |
gr-qc hep-th math-ph math.MP
| null |
A new approach to quantize the gravitational field is presented. It is based
on the observation that the quantum character of matter becomes more
significant as one gets closer to the big bang. As the metric loses its
meaning, it makes sense to consider Schrodinger's three generic types of
manifolds - unconnected differentiable, affinely connected, and metrically
connected - as a temporal sequence following the big bang. Hence one should
quantize the gravitational field on general differentiable manifolds or on
affinely connected manifolds. The SL(2,C) gauge theory of gravitation is
employed to explore this possibility. Within this framework, the quantization
itself may well be canonical.
|
[
{
"created": "Sun, 25 Jul 1999 06:23:19 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Carmeli",
"Moshe",
"",
"Ben Gurion U."
],
[
"Malin",
"Shimon",
"",
"Colgate U."
]
] |
A new approach to quantize the gravitational field is presented. It is based on the observation that the quantum character of matter becomes more significant as one gets closer to the big bang. As the metric loses its meaning, it makes sense to consider Schrodinger's three generic types of manifolds - unconnected differentiable, affinely connected, and metrically connected - as a temporal sequence following the big bang. Hence one should quantize the gravitational field on general differentiable manifolds or on affinely connected manifolds. The SL(2,C) gauge theory of gravitation is employed to explore this possibility. Within this framework, the quantization itself may well be canonical.
|
1502.01907
|
Emma Jakobsson
|
Ingemar Bengtsson and Emma Jakobsson
|
Black holes: Their large interiors
|
6 pages, 2 figures. To appear in Modern Physics Letters A
|
Mod. Phys. Lett. A, Vol. 30, No. 21 (2015) 1550103
|
10.1142/S0217732315501035
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Christodoulou and Rovelli have remarked on the large interiors possessed by
static black holes. We amplify their remarks, and extend them to the spinning
case.
|
[
{
"created": "Fri, 6 Feb 2015 14:51:40 GMT",
"version": "v1"
},
{
"created": "Fri, 20 Mar 2015 15:32:31 GMT",
"version": "v2"
}
] |
2015-08-19
|
[
[
"Bengtsson",
"Ingemar",
""
],
[
"Jakobsson",
"Emma",
""
]
] |
Christodoulou and Rovelli have remarked on the large interiors possessed by static black holes. We amplify their remarks, and extend them to the spinning case.
|
gr-qc/0302053
|
Gaetano Lambiase
|
G. Lambiase
|
Spin Flavor Conversion of Neutrinos in Loop Quantum Gravity
|
7 pages, no figure
|
Class.Quant.Grav. 20 (2003) 4213-4220
|
10.1088/0264-9381/20/19/306
| null |
gr-qc hep-ph
| null |
Loop quantum gravity theory incorporates a new scale length ${\cal L}$ which
induces a Lorentz invariance breakdown. This scale can be either an universal
constant or can be fixed by the momentum of particles (${\cal L}\sim p^{-1}$).
Effects of the scale parameter ${\cal L}$ and helicity terms occurring in the
dispersion relation of fermions are reviewed in the framework of spin-flip
conversion of neutrino flavors.
|
[
{
"created": "Thu, 13 Feb 2003 13:49:15 GMT",
"version": "v1"
}
] |
2016-08-31
|
[
[
"Lambiase",
"G.",
""
]
] |
Loop quantum gravity theory incorporates a new scale length ${\cal L}$ which induces a Lorentz invariance breakdown. This scale can be either an universal constant or can be fixed by the momentum of particles (${\cal L}\sim p^{-1}$). Effects of the scale parameter ${\cal L}$ and helicity terms occurring in the dispersion relation of fermions are reviewed in the framework of spin-flip conversion of neutrino flavors.
|
1412.6789
|
Raissa Mendes
|
Raissa F. P. Mendes
|
On the possibility of setting a new constraint to scalar-tensor theories
|
8 pages, 4 figures; matches published version
|
PRD 91, 064024 (2015)
|
10.1103/PhysRevD.91.064024
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Scalar-tensor theories (STTs) are a widely studied alternative to General
Relativity (GR) in which gravity is endowed with an additional scalar degree of
freedom. Although severely constrained by solar system and pulsar timing
experiments, there remains a large set of STTs which are consistent with all
present day observations. In this paper, we investigate the possibility of
probing a yet unconstrained region of the parameter space of STTs based on the
fact that stability properties of highly compact neutron stars in these
theories may radically differ from those in GR.
|
[
{
"created": "Sun, 21 Dec 2014 14:30:19 GMT",
"version": "v1"
},
{
"created": "Thu, 12 Mar 2015 17:41:45 GMT",
"version": "v2"
}
] |
2015-03-13
|
[
[
"Mendes",
"Raissa F. P.",
""
]
] |
Scalar-tensor theories (STTs) are a widely studied alternative to General Relativity (GR) in which gravity is endowed with an additional scalar degree of freedom. Although severely constrained by solar system and pulsar timing experiments, there remains a large set of STTs which are consistent with all present day observations. In this paper, we investigate the possibility of probing a yet unconstrained region of the parameter space of STTs based on the fact that stability properties of highly compact neutron stars in these theories may radically differ from those in GR.
|
gr-qc/9710037
|
Luc Blanchet
|
Luc Blanchet
|
Quadrupole-quadrupole gravitational waves
|
contains 3 files: a tex file grq97quad.tex and 2 latex files for the
tables: tabbquad.tex and 2tabbqua.tex, to appear in Classical and Quantum
Gravity
|
Class.Quant.Grav. 15 (1998) 89-111
|
10.1088/0264-9381/15/1/008
| null |
gr-qc
| null |
This paper investigates the non-linear self-interaction of quadrupole
gravitational waves generated by an isolated system. The vacuum Einstein field
equations are integrated in the region exterior to the system by means of a
post-Minkowskian algorithm. Specializing in the quadrupole-quadrupole
interaction (at the quadratic non-linear order), we recover the known results
concerning the non-local modification of the ADM mass-energy of the system
accounting for the emission of quadrupole waves, and the non-local memory
effect due to the re-radiation by the stress-energy distribution of linear
waves. Then we compute all the local (instantaneous) terms which are associated
in the quadrupole-quadrupole metric with the latter non-local effects.
Expanding the metric at large distances from the system, we obtain the
corresponding radiation-field observables, including all non-local and
transient contributions. This permits notably the completion of the observable
quadrupole moment at the 5/2 post-Newtonian order.
|
[
{
"created": "Tue, 7 Oct 1997 09:44:22 GMT",
"version": "v1"
}
] |
2009-10-30
|
[
[
"Blanchet",
"Luc",
""
]
] |
This paper investigates the non-linear self-interaction of quadrupole gravitational waves generated by an isolated system. The vacuum Einstein field equations are integrated in the region exterior to the system by means of a post-Minkowskian algorithm. Specializing in the quadrupole-quadrupole interaction (at the quadratic non-linear order), we recover the known results concerning the non-local modification of the ADM mass-energy of the system accounting for the emission of quadrupole waves, and the non-local memory effect due to the re-radiation by the stress-energy distribution of linear waves. Then we compute all the local (instantaneous) terms which are associated in the quadrupole-quadrupole metric with the latter non-local effects. Expanding the metric at large distances from the system, we obtain the corresponding radiation-field observables, including all non-local and transient contributions. This permits notably the completion of the observable quadrupole moment at the 5/2 post-Newtonian order.
|
1504.01266
|
Tim Dietrich
|
Tim Dietrich, Sebastiano Bernuzzi, Maximiliano Ujevic, Bernd Bruegmann
|
Numerical relativity simulations of neutron star merger remnants using
conservative mesh refinement
|
26 pages, 18 figures
|
Phys. Rev. D 91, 124041 (2015)
|
10.1103/PhysRevD.91.124041
| null |
gr-qc astro-ph.HE astro-ph.SR
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study equal and unequal-mass neutron star mergers by means of new
numerical relativity simulations in which the general relativistic
hydrodynamics solver employs an algorithm that guarantees mass conservation
across the refinement levels of the computational mesh. We consider eight
binary configurations with total mass $M=2.7\,M_\odot$, mass-ratios $q=1$ and
$q=1.16$, and four different equation of states (EOSs), and one configuration
with a stiff EOS, $M=2.5M_\odot$ and $q=1.5$. We focus on the post-merger
dynamics and study the merger remnant, dynamical ejecta and the postmerger
gravitational wave spectrum. Although most of the merger remnants form a
hypermassive neutron star collapsing to a black hole+disk system on dynamical
timescales, stiff EOSs can eventually produce a stable massive neutron star.
Ejecta are mostly emitted around the orbital plane; favored by large mass
ratios and softer EOS. The postmerger wave spectrum is mainly characterized by
non-axisymmetric oscillations of the remnant. The stiff EOS configuration
consisting of a $1.5M_\odot$ and a $1.0M_\odot$ neutron star shows a rather
peculiar dynamics. During merger the companion star is very deformed;
about~$\sim0.03M_\odot$ of rest-mass becomes unbound from the tidal tail due
torque; and the merger remnant forms stable neutron star surrounded by a
massive accretion disk $\sim0.3M_\odot$. Similar configurations might be
particularly interesting for electromagnetic counterparts. Comparing results
obtained with and without the conservative mesh refinement algorithm, we find
that post-merger simulations can be affected by systematic errors if mass
conservation is not enforced in the mesh refinement strategy. However, mass
conservation also depends on grid details and on the artificial atmosphere
setup. [abridged]
|
[
{
"created": "Mon, 6 Apr 2015 11:34:31 GMT",
"version": "v1"
}
] |
2015-06-17
|
[
[
"Dietrich",
"Tim",
""
],
[
"Bernuzzi",
"Sebastiano",
""
],
[
"Ujevic",
"Maximiliano",
""
],
[
"Bruegmann",
"Bernd",
""
]
] |
We study equal and unequal-mass neutron star mergers by means of new numerical relativity simulations in which the general relativistic hydrodynamics solver employs an algorithm that guarantees mass conservation across the refinement levels of the computational mesh. We consider eight binary configurations with total mass $M=2.7\,M_\odot$, mass-ratios $q=1$ and $q=1.16$, and four different equation of states (EOSs), and one configuration with a stiff EOS, $M=2.5M_\odot$ and $q=1.5$. We focus on the post-merger dynamics and study the merger remnant, dynamical ejecta and the postmerger gravitational wave spectrum. Although most of the merger remnants form a hypermassive neutron star collapsing to a black hole+disk system on dynamical timescales, stiff EOSs can eventually produce a stable massive neutron star. Ejecta are mostly emitted around the orbital plane; favored by large mass ratios and softer EOS. The postmerger wave spectrum is mainly characterized by non-axisymmetric oscillations of the remnant. The stiff EOS configuration consisting of a $1.5M_\odot$ and a $1.0M_\odot$ neutron star shows a rather peculiar dynamics. During merger the companion star is very deformed; about~$\sim0.03M_\odot$ of rest-mass becomes unbound from the tidal tail due torque; and the merger remnant forms stable neutron star surrounded by a massive accretion disk $\sim0.3M_\odot$. Similar configurations might be particularly interesting for electromagnetic counterparts. Comparing results obtained with and without the conservative mesh refinement algorithm, we find that post-merger simulations can be affected by systematic errors if mass conservation is not enforced in the mesh refinement strategy. However, mass conservation also depends on grid details and on the artificial atmosphere setup. [abridged]
|
1912.13128
|
Vasilis Oikonomou
|
Shin'ichi Nojiri, Sergei D. Odintsov, V.K. Oikonomou
|
Unifying Inflation with Early and Late-time Dark Energy in $F(R)$
Gravity
|
Revised Version, PDU Accepted
| null | null | null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work we shall present models of $F(R)$ gravity which realize in a
unified way the inflationary era along with a post-inflationary early dark
energy era, with the late-time dark energy era. We shall use two approach
methods in order to realize the unified cosmological eras, firstly we specify a
Hubble rate which may describe the three distinct acceleration eras, and then
by using well known $F(R)$ gravity reconstruction techniques, we shall find the
differential equation which may yield the $F(R)$ gravity that realizes the
cosmologies. In our second approach, we shall present in a qualitative way,
several $F(R)$ gravities which unify the inflationary era with the early and
late-time dark energy eras, and we discuss several qualitative issues related
to the terms that realize the post-inflationary early dark energy era. We
quantify our analysis by numerically solving the Friedmann equation, using the
redshift as the main variable, and expressing all the physical quantities as
functions of the statefinder $y_\mathrm{H}(z)$, which depends on the redshift
and the Hubble rate $H(z)$. For the model studied numerically, we present the
behavior of some statefinder quantities, like the deceleration parameter, and
we calculate the dark energy density parameter and the dark energy equation of
state parameter at present time. After demonstrating that the dark energy era
is viable, we investigate when the early dark energy term does not affect the
late-time era, and this restricts the free parameters of the model.
|
[
{
"created": "Tue, 31 Dec 2019 00:50:46 GMT",
"version": "v1"
},
{
"created": "Tue, 26 May 2020 15:52:50 GMT",
"version": "v2"
}
] |
2020-05-27
|
[
[
"Nojiri",
"Shin'ichi",
""
],
[
"Odintsov",
"Sergei D.",
""
],
[
"Oikonomou",
"V. K.",
""
]
] |
In this work we shall present models of $F(R)$ gravity which realize in a unified way the inflationary era along with a post-inflationary early dark energy era, with the late-time dark energy era. We shall use two approach methods in order to realize the unified cosmological eras, firstly we specify a Hubble rate which may describe the three distinct acceleration eras, and then by using well known $F(R)$ gravity reconstruction techniques, we shall find the differential equation which may yield the $F(R)$ gravity that realizes the cosmologies. In our second approach, we shall present in a qualitative way, several $F(R)$ gravities which unify the inflationary era with the early and late-time dark energy eras, and we discuss several qualitative issues related to the terms that realize the post-inflationary early dark energy era. We quantify our analysis by numerically solving the Friedmann equation, using the redshift as the main variable, and expressing all the physical quantities as functions of the statefinder $y_\mathrm{H}(z)$, which depends on the redshift and the Hubble rate $H(z)$. For the model studied numerically, we present the behavior of some statefinder quantities, like the deceleration parameter, and we calculate the dark energy density parameter and the dark energy equation of state parameter at present time. After demonstrating that the dark energy era is viable, we investigate when the early dark energy term does not affect the late-time era, and this restricts the free parameters of the model.
|
2305.10815
|
Mert Mangut
|
M. Mangut, H. G\"ursel, S. Kanzi and \.I. Sakall{\i}
|
Probing the Lorentz Invariance Violation via Gravitational Lensing and
Analytical Eigenmodes of Perturbed Slowly Rotating Bumblebee Black Holes
| null |
Universe, 2023
|
10.3390/universe9050225
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The ability of bumblebee gravity models to explain dark energy, which is the
phenomenon responsible for the universe's observed accelerated expansion, is
one of their most significant applications. An effect that causes faster
expansion can be linked to how much the Lorentz symmetry of our universe is
violated. Moreover, since we do not know what generates dark energy, the
bumblebee gravity theory seems highly plausible. By utilizing the physical
changes happening around a rotating bumblebee black hole (RBBH), we aim to
obtain more specific details about the bumblebee black hole's spacetime and our
universe. However, as researched in the literature, slow-spinning RBBH (SRBBH)
spacetime, which has a higher accuracy, will be considered instead of general
RBBH. To this end, we first employ the Rindler--Ishak method (RIM), which
enables us to study how light is bent in the vicinity of a gravitational lens.
We evaluate the deflection angle of null geodesics in the equatorial plane of
the SRBBH spacetime. Then, we use astrophysical data to see the effect of the
Lorentz symmetry breaking (LSB) parameter on the bending angle of light for
numerous astrophysical stars and black holes. We also acquire the analytical
greybody factors (GFs) and quasinormal modes (QNMs) of the SRBBH. Finally, we
visualize and discuss the results obtained in the conclusion section.
|
[
{
"created": "Thu, 18 May 2023 08:52:11 GMT",
"version": "v1"
}
] |
2023-05-19
|
[
[
"Mangut",
"M.",
""
],
[
"Gürsel",
"H.",
""
],
[
"Kanzi",
"S.",
""
],
[
"Sakallı",
"İ.",
""
]
] |
The ability of bumblebee gravity models to explain dark energy, which is the phenomenon responsible for the universe's observed accelerated expansion, is one of their most significant applications. An effect that causes faster expansion can be linked to how much the Lorentz symmetry of our universe is violated. Moreover, since we do not know what generates dark energy, the bumblebee gravity theory seems highly plausible. By utilizing the physical changes happening around a rotating bumblebee black hole (RBBH), we aim to obtain more specific details about the bumblebee black hole's spacetime and our universe. However, as researched in the literature, slow-spinning RBBH (SRBBH) spacetime, which has a higher accuracy, will be considered instead of general RBBH. To this end, we first employ the Rindler--Ishak method (RIM), which enables us to study how light is bent in the vicinity of a gravitational lens. We evaluate the deflection angle of null geodesics in the equatorial plane of the SRBBH spacetime. Then, we use astrophysical data to see the effect of the Lorentz symmetry breaking (LSB) parameter on the bending angle of light for numerous astrophysical stars and black holes. We also acquire the analytical greybody factors (GFs) and quasinormal modes (QNMs) of the SRBBH. Finally, we visualize and discuss the results obtained in the conclusion section.
|
2302.08812
|
Sergi Nadal-Gisbert
|
Sergi Nadal-Gisbert, Jos\'e Navarro-Salas and Silvia Pla
|
Low Energy States and CPT invariance at the Big Bang
|
21 pages
| null |
10.1103/PhysRevD.107.085018
| null |
gr-qc hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we analyze the quantum vacuum in a radiation-dominated and
CPT-invariant universe by further imposing the quantum states to be ultraviolet
regular i.e., satisfying the Hadamard/adiabatic condition. For scalar fields,
this is enforced by constructing the vacuum via the States of Low Energy
proposal. For spin-$\frac{1}{2}$ fields, we extend this proposal for a FLRW
spacetime and apply it for the radiation-dominated and CPT-invariant universe.
We focus on minimizing the smeared energy density around the Big Bang and give
strong evidence that the resulting states satisfy the Hadamard/adiabatic
condition. These states are then self-consistent candidates as effective Big
Bang quantum vacuum from the field theory perspective.
|
[
{
"created": "Fri, 17 Feb 2023 11:12:01 GMT",
"version": "v1"
}
] |
2023-05-10
|
[
[
"Nadal-Gisbert",
"Sergi",
""
],
[
"Navarro-Salas",
"José",
""
],
[
"Pla",
"Silvia",
""
]
] |
In this paper, we analyze the quantum vacuum in a radiation-dominated and CPT-invariant universe by further imposing the quantum states to be ultraviolet regular i.e., satisfying the Hadamard/adiabatic condition. For scalar fields, this is enforced by constructing the vacuum via the States of Low Energy proposal. For spin-$\frac{1}{2}$ fields, we extend this proposal for a FLRW spacetime and apply it for the radiation-dominated and CPT-invariant universe. We focus on minimizing the smeared energy density around the Big Bang and give strong evidence that the resulting states satisfy the Hadamard/adiabatic condition. These states are then self-consistent candidates as effective Big Bang quantum vacuum from the field theory perspective.
|
1703.00610
|
Rafael Sorkin
|
Rafael D. Sorkin
|
From Green Function to Quantum Field
|
plainTeX, 29 pages, 7 figures. Most current version is available at
http://www.perimeterinstitute.ca/personal/rsorkin/some.papers/157.G2f.pdf (or
wherever my home-page may be, such as
http://www.physics.syr.edu/~sorkin/some.papers/)
| null |
10.1142/S0219887817400072
| null |
gr-qc hep-th math-ph math.MP quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A pedagogical introduction to the theory of a gaussian scalar field which
shows firstly, how the whole theory is encapsulated in the Wightman function
$W(x,y)=\langle\phi(x)\phi(y)\rangle$ regarded abstractly as a two-index tensor
on the vector space of (spacetime) field configurations, and secondly how one
can arrive at $W(x,y)$ starting from nothing but the retarded Green function
$G(x,y)$. Conceiving the theory in this manner seems well suited to curved
spacetimes and to causal sets. It makes it possible to provide a general
spacetime region with a distinguished "vacuum" or "ground state", and to
recognize some interesting formal relationships, including a general condition
on $W(x,y)$ expressing zero-entropy or "purity".
|
[
{
"created": "Thu, 2 Mar 2017 04:19:11 GMT",
"version": "v1"
}
] |
2017-08-02
|
[
[
"Sorkin",
"Rafael D.",
""
]
] |
A pedagogical introduction to the theory of a gaussian scalar field which shows firstly, how the whole theory is encapsulated in the Wightman function $W(x,y)=\langle\phi(x)\phi(y)\rangle$ regarded abstractly as a two-index tensor on the vector space of (spacetime) field configurations, and secondly how one can arrive at $W(x,y)$ starting from nothing but the retarded Green function $G(x,y)$. Conceiving the theory in this manner seems well suited to curved spacetimes and to causal sets. It makes it possible to provide a general spacetime region with a distinguished "vacuum" or "ground state", and to recognize some interesting formal relationships, including a general condition on $W(x,y)$ expressing zero-entropy or "purity".
|
1702.07291
|
Antonio Troisi
|
Antonio Troisi
|
Higher-order gravity in higher dimensions: Geometrical origins of
four-dimensional cosmology?
|
18 pages, 4 figures; accepted for publication in EPJC
| null |
10.1140/epjc/s10052-017-4719-7
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Determining cosmological field equations represents a still very debated
matter and implies a wide discussion around different theoretical proposals. A
suitable conceptual scheme could be represented by gravity models that
naturally generalize Einstein Theory like higher order gravity theories and
higher dimensional ones. Both of these two different approaches allow to
define, at the effective level, Einstein field equations equipped with
source-like energy momentum tensors of geometrical origin. In this paper, it is
discussed the possibility to develop a five dimensional fourth order gravity
model whose lower dimensional reduction could provide an interpretation of
cosmological four dimensional matter-energy components. We describe the basic
concepts of the model, the complete field equations formalism and the 5-Dim to
4-Dim reduction procedure. Five dimensional $f(R)$ field equations turn out to
be equivalent, on the four dimensional hypersurfaces orthogonal to the
extra-coordinate, to an Einstein like cosmological model with three
matter-energy tensors related with higher derivative and higher dimensional
counter-terms. By considering a gravity model $f(R)=f_0R^n$ it is investigated
the possibility to obtain five dimensional power law solutions. The effective
four dimensional picture and the behaviour of the geometrically induced sources
are finally outlined in correspondence to simple cases of such higher
dimensional solutions.
|
[
{
"created": "Thu, 23 Feb 2017 16:54:30 GMT",
"version": "v1"
}
] |
2017-04-05
|
[
[
"Troisi",
"Antonio",
""
]
] |
Determining cosmological field equations represents a still very debated matter and implies a wide discussion around different theoretical proposals. A suitable conceptual scheme could be represented by gravity models that naturally generalize Einstein Theory like higher order gravity theories and higher dimensional ones. Both of these two different approaches allow to define, at the effective level, Einstein field equations equipped with source-like energy momentum tensors of geometrical origin. In this paper, it is discussed the possibility to develop a five dimensional fourth order gravity model whose lower dimensional reduction could provide an interpretation of cosmological four dimensional matter-energy components. We describe the basic concepts of the model, the complete field equations formalism and the 5-Dim to 4-Dim reduction procedure. Five dimensional $f(R)$ field equations turn out to be equivalent, on the four dimensional hypersurfaces orthogonal to the extra-coordinate, to an Einstein like cosmological model with three matter-energy tensors related with higher derivative and higher dimensional counter-terms. By considering a gravity model $f(R)=f_0R^n$ it is investigated the possibility to obtain five dimensional power law solutions. The effective four dimensional picture and the behaviour of the geometrically induced sources are finally outlined in correspondence to simple cases of such higher dimensional solutions.
|
gr-qc/0702068
|
Reinhard Prix
|
Reinhard Prix
|
Search for Continuous Gravitational Waves: simple criterion for optimal
detector networks
|
3 pages, 2 figures; Proceedings of the 11th Marcel-Grossmann Meeting
(MG11)
| null |
10.1142/9789812834300_0429
| null |
gr-qc
| null |
We derive a simple algebraic criterion to select the optimal detector network
for a coherent wide parameter-space (all-sky) search for continuous
gravitational waves. Optimality in this context is defined as providing the
highest (average) sensitivity per computing cost. This criterion is a direct
consequence of the properties of the multi-detector F-statistic metric, which
has been derived recently. Interestingly, the choice of the optimal network
only depends on the noise-levels and duty-cycles of the respective detectors,
and not on the available computing power.
|
[
{
"created": "Mon, 12 Feb 2007 12:46:22 GMT",
"version": "v1"
}
] |
2016-11-15
|
[
[
"Prix",
"Reinhard",
""
]
] |
We derive a simple algebraic criterion to select the optimal detector network for a coherent wide parameter-space (all-sky) search for continuous gravitational waves. Optimality in this context is defined as providing the highest (average) sensitivity per computing cost. This criterion is a direct consequence of the properties of the multi-detector F-statistic metric, which has been derived recently. Interestingly, the choice of the optimal network only depends on the noise-levels and duty-cycles of the respective detectors, and not on the available computing power.
|
0712.3419
|
Craig J. Hogan
|
Craig J. Hogan
|
Measurement of Quantum Fluctuations in Geometry
|
7 pages, 2 figures, LaTeX. Extensive rewrite of original version,
including more detailed analysis. Main result is the same but the estimate of
noise in strain units for GEO600, showing 1/f behavior at low f and flat at
high f, is improved. To appear in Phys. Rev. D
|
Phys.Rev.D77:104031,2008
|
10.1103/PhysRevD.77.104031
| null |
gr-qc astro-ph hep-ph
| null |
A particular form for the quantum indeterminacy of relative spacetime
position of events is derived from the limits of measurement possible with
Planck wavelength radiation. The indeterminacy predicts fluctuations from a
classically defined geometry in the form of ``holographic noise'' whose spatial
character, absolute normalization, and spectrum are predicted with no
parameters. The noise has a distinctive transverse spatial shear signature, and
a flat power spectral density given by the Planck time. An interferometer
signal displays noise due to the uncertainty of relative positions of
reflection events. The noise corresponds to an accumulation of phase offset
with time that mimics a random walk of those optical elements that change the
orientation of a wavefront. It only appears in measurements that compare
transverse positions, and does not appear at all in purely radial position
measurements. A lower bound on holographic noise follows from a covariant upper
bound on gravitational entropy. The predicted holographic noise spectrum is
estimated to be comparable to measured noise in the currently operating
interferometer GEO600. Because of its transverse character, holographic noise
is reduced relative to gravitational wave effects in other interferometer
designs, such as LIGO, where beam power is much less in the beamsplitter than
in the arms.
|
[
{
"created": "Thu, 20 Dec 2007 13:48:00 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jan 2008 17:50:20 GMT",
"version": "v2"
},
{
"created": "Mon, 28 Jan 2008 02:03:21 GMT",
"version": "v3"
},
{
"created": "Fri, 1 Feb 2008 14:53:10 GMT",
"version": "v4"
},
{
"created": "Mon, 24 Mar 2008 11:30:55 GMT",
"version": "v5"
}
] |
2008-11-26
|
[
[
"Hogan",
"Craig J.",
""
]
] |
A particular form for the quantum indeterminacy of relative spacetime position of events is derived from the limits of measurement possible with Planck wavelength radiation. The indeterminacy predicts fluctuations from a classically defined geometry in the form of ``holographic noise'' whose spatial character, absolute normalization, and spectrum are predicted with no parameters. The noise has a distinctive transverse spatial shear signature, and a flat power spectral density given by the Planck time. An interferometer signal displays noise due to the uncertainty of relative positions of reflection events. The noise corresponds to an accumulation of phase offset with time that mimics a random walk of those optical elements that change the orientation of a wavefront. It only appears in measurements that compare transverse positions, and does not appear at all in purely radial position measurements. A lower bound on holographic noise follows from a covariant upper bound on gravitational entropy. The predicted holographic noise spectrum is estimated to be comparable to measured noise in the currently operating interferometer GEO600. Because of its transverse character, holographic noise is reduced relative to gravitational wave effects in other interferometer designs, such as LIGO, where beam power is much less in the beamsplitter than in the arms.
|
gr-qc/0107030
|
Leo Brewin
|
Leo Brewin
|
Long term stable integration of a maximally sliced Schwarzschild black
hole using a smooth lattice method
|
47 pages including 26 figures, plain TeX, also available at
http://www.maths.monash.edu.au/~leo/preprints
|
Class.Quant.Grav. 19 (2002) 429-456
|
10.1088/0264-9381/19/3/302
| null |
gr-qc
| null |
We will present results of a numerical integration of a maximally sliced
Schwarzschild black hole using a smooth lattice method. The results show no
signs of any instability forming during the evolutions to t=1000m. The
principle features of our method are i) the use of a lattice to record the
geometry, ii) the use of local Riemann normal coordinates to apply the 1+1 ADM
equations to the lattice and iii) the use of the Bianchi identities to assist
in the computation of the curvatures. No other special techniques are used. The
evolution is unconstrained and the ADM equations are used in their standard
form.
|
[
{
"created": "Tue, 10 Jul 2001 05:30:54 GMT",
"version": "v1"
}
] |
2009-11-07
|
[
[
"Brewin",
"Leo",
""
]
] |
We will present results of a numerical integration of a maximally sliced Schwarzschild black hole using a smooth lattice method. The results show no signs of any instability forming during the evolutions to t=1000m. The principle features of our method are i) the use of a lattice to record the geometry, ii) the use of local Riemann normal coordinates to apply the 1+1 ADM equations to the lattice and iii) the use of the Bianchi identities to assist in the computation of the curvatures. No other special techniques are used. The evolution is unconstrained and the ADM equations are used in their standard form.
|
2407.20567
|
Adam Rogers
|
Adam Rogers
|
Ray Tracing Through Absorbing Dielectric Media in the Schwarzschild
Spacetime
|
Comments Welcome!
|
Class. Quantum Grav., 2024, 41, 17
|
10.1088/1361-6382/ad64a5
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
General Relativity describes the trajectories of light-rays through curved
spacetime near a massive object. In addition to gravitational lensing, we
include an absorbing dielectric medium given by a complex refractive index
known as the Drude model. When absorption is included the eikonal becomes
complex, with the imaginary part related to the absorption along a ray between
emission and observation points. We extend results from the literature to
include dispersion in the index of refraction. The complex Hamiltonian splits
into a real part that describes the equations of motion and a constraint
equation that governs the momentum loss in the system. We work in coordinates
which are fully real, with a real metric in physical spacetime. We assume the
dust and plasma distributions of the Drude matter to coincide and vary as a
power-law $1/r^h$. We find that transmission requires $h>1$, otherwise
exponential absorption occurs along ray paths. We use ray-tracing through
strongly absorbing matter near the surface of the compact star, as well as
specializing to a point-lens in the weak-field limit with weakly absorbing
matter to generate potentially observable light curves for distant observers.
In the appropriate limits, our theory reproduces results from the literature.
|
[
{
"created": "Tue, 30 Jul 2024 05:52:39 GMT",
"version": "v1"
}
] |
2024-07-31
|
[
[
"Rogers",
"Adam",
""
]
] |
General Relativity describes the trajectories of light-rays through curved spacetime near a massive object. In addition to gravitational lensing, we include an absorbing dielectric medium given by a complex refractive index known as the Drude model. When absorption is included the eikonal becomes complex, with the imaginary part related to the absorption along a ray between emission and observation points. We extend results from the literature to include dispersion in the index of refraction. The complex Hamiltonian splits into a real part that describes the equations of motion and a constraint equation that governs the momentum loss in the system. We work in coordinates which are fully real, with a real metric in physical spacetime. We assume the dust and plasma distributions of the Drude matter to coincide and vary as a power-law $1/r^h$. We find that transmission requires $h>1$, otherwise exponential absorption occurs along ray paths. We use ray-tracing through strongly absorbing matter near the surface of the compact star, as well as specializing to a point-lens in the weak-field limit with weakly absorbing matter to generate potentially observable light curves for distant observers. In the appropriate limits, our theory reproduces results from the literature.
|
2407.08327
|
Zihan Zhou
|
M. V. S. Saketh, Zihan Zhou, Suprovo Ghosh, Jan Steinhoff, Debarati
Chatterjee
|
Investigating tidal heating in neutron stars via gravitational Raman
scattering
|
28 pages, 2 tables, 1 appendix, version 2
| null | null | null |
gr-qc astro-ph.HE hep-ph hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
We present a scattering amplitude formalism to study the tidal heating
effects of nonspinning neutron stars incorporating both worldline effective
field theory and relativistic stellar perturbation theory. In neutron stars,
tidal heating arises from fluid viscosity due to various scattering processes
in the interior. It also serves as a channel for the exchange of energy and
angular momentum between the neutron star and its environment. In the interior
of the neutron star, we first derive two master perturbation equations that
capture fluid perturbations accurate to linear order in frequency. Remarkably,
these equations receive no contribution from bulk viscosity due to a peculiar
adiabatic incompressibility which arises in stellar fluid for non-barotropic
perturbations. In the exterior, the metric perturbations reduce to the
Regge-Wheeler (RW) equation which we solve using the analytical
Mano-Suzuki-Takasugi (MST) method. We compute the amplitude for gravitational
waves scattering off a neutron star, also known as gravitational Raman
scattering. From the amplitude, we obtain expressions for the electric
quadrupolar static Love number and the leading dissipation number to all orders
in compactness. We then compute the leading dissipation number for various
realistic equation-of-state(s) and estimate the change in the number of
gravitational wave cycles due to tidal heating during inspiral in the
LIGO-Virgo-KAGRA (LVK) band.
|
[
{
"created": "Thu, 11 Jul 2024 09:26:04 GMT",
"version": "v1"
},
{
"created": "Fri, 26 Jul 2024 17:42:14 GMT",
"version": "v2"
}
] |
2024-07-29
|
[
[
"Saketh",
"M. V. S.",
""
],
[
"Zhou",
"Zihan",
""
],
[
"Ghosh",
"Suprovo",
""
],
[
"Steinhoff",
"Jan",
""
],
[
"Chatterjee",
"Debarati",
""
]
] |
We present a scattering amplitude formalism to study the tidal heating effects of nonspinning neutron stars incorporating both worldline effective field theory and relativistic stellar perturbation theory. In neutron stars, tidal heating arises from fluid viscosity due to various scattering processes in the interior. It also serves as a channel for the exchange of energy and angular momentum between the neutron star and its environment. In the interior of the neutron star, we first derive two master perturbation equations that capture fluid perturbations accurate to linear order in frequency. Remarkably, these equations receive no contribution from bulk viscosity due to a peculiar adiabatic incompressibility which arises in stellar fluid for non-barotropic perturbations. In the exterior, the metric perturbations reduce to the Regge-Wheeler (RW) equation which we solve using the analytical Mano-Suzuki-Takasugi (MST) method. We compute the amplitude for gravitational waves scattering off a neutron star, also known as gravitational Raman scattering. From the amplitude, we obtain expressions for the electric quadrupolar static Love number and the leading dissipation number to all orders in compactness. We then compute the leading dissipation number for various realistic equation-of-state(s) and estimate the change in the number of gravitational wave cycles due to tidal heating during inspiral in the LIGO-Virgo-KAGRA (LVK) band.
|
2401.07846
|
Naoki Tsukamoto
|
Naoki Tsukamoto
|
Circular light orbits of a general, static, and spherical symmetrical
wormhole with $Z_2$ symmetry
|
11 pages, 5 figures, minor correction
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
A general asymptotically-flat, static, and spherical symmetrical wormhole
without a thin shell has at least one unstable circular light orbit at a
radius. If the wormhole has $Z_2$ symmetry against the throat, the stable or
unstable circular light orbit must be on the throat but this fact is often
overlooked. In this study, we categorize the numbers of the circular light
orbits of the $Z_2$-symmetrical wormhole and their stability from the
derivatives of an effective potential at the throat and we investigate the
circular light orbits around a Simpson-Visser black-bounce spacetime, a
DamourSolodukhin wormhole spacetime, a Reissner-Nordstr\"{o}m black-hole-like
wormhole spacetime or a charged Damour-Solodukhin wormhole spacetime as
examples. We give complete treaments including degenerated circular light
orbits made from more than one stable and unstable circular light orbits on and
off the throat.
|
[
{
"created": "Mon, 15 Jan 2024 17:22:46 GMT",
"version": "v1"
},
{
"created": "Tue, 6 Feb 2024 08:05:55 GMT",
"version": "v2"
},
{
"created": "Sun, 23 Jun 2024 10:15:19 GMT",
"version": "v3"
}
] |
2024-06-25
|
[
[
"Tsukamoto",
"Naoki",
""
]
] |
A general asymptotically-flat, static, and spherical symmetrical wormhole without a thin shell has at least one unstable circular light orbit at a radius. If the wormhole has $Z_2$ symmetry against the throat, the stable or unstable circular light orbit must be on the throat but this fact is often overlooked. In this study, we categorize the numbers of the circular light orbits of the $Z_2$-symmetrical wormhole and their stability from the derivatives of an effective potential at the throat and we investigate the circular light orbits around a Simpson-Visser black-bounce spacetime, a DamourSolodukhin wormhole spacetime, a Reissner-Nordstr\"{o}m black-hole-like wormhole spacetime or a charged Damour-Solodukhin wormhole spacetime as examples. We give complete treaments including degenerated circular light orbits made from more than one stable and unstable circular light orbits on and off the throat.
|
2210.16983
|
Shinji Tsujikawa
|
Ratchaphat Nakarachinda, Sirachak Panpanich, Shinji Tsujikawa,
Pitayuth Wongjun
|
Cosmology in theories with spontaneous scalarization of neutron stars
|
15 pages, 8 figures
|
Phys. Rev. D 107, 043512 (2023)
|
10.1103/PhysRevD.107.043512
|
WUCG-22-10
|
gr-qc astro-ph.CO hep-ph hep-th
|
http://creativecommons.org/licenses/by/4.0/
|
In a model of spontaneous scalarization of neutron stars proposed by Damour
and Esposite-Farese, a general relativistic branch becomes unstable to trigger
tachyonic growth of a scalar field $\phi$ toward a scalarized branch. Applying
this scenario to cosmology, there is fatal tachyonic instability of $\phi$
during inflation and matter dominance being incompatible with solar-system
constraints on today's field value $\phi_0$. In the presence of a four-point
coupling $g^2 \phi^2 \chi^2/2$ between $\phi$ and an inflaton field $\chi$, it
was argued by Anson et al. that a positive mass squared heavier than the square
of a Hubble expansion rate leads to the exponential suppression of $\phi$
during inflation and that $\phi_0$ can remain small even with the growth of
$\phi$ after the radiation-dominated epoch. For several inflaton potentials
approximated as $V(\chi)=m^2 \chi^2/2$ about the potential minimum, we study
the dynamics of $\phi$ during reheating as well as other cosmological epochs in
detail. For certain ranges of the coupling $g$, the homogeneous field $\phi$
can be amplified by parametric resonance during a coherent oscillation of the
inflaton. Incorporating the backreaction of created particles under a Hartree
approximation, the maximum values of $\phi$ reached during preheating are
significantly smaller than those obtained without the backreaction. We also
find that the minimum values of $g$ consistent with solar system bounds on
$\phi$ at the end of reheating are of order $10^{-5}$ and hence there is a wide
range of acceptable values of $g$. Thus, the scenario proposed by Anson et al.
naturally leads to the viable cosmological evolution of $\phi$ consistent with
local gravity constraints, without modifying the property of scalarized neutron
stars.
|
[
{
"created": "Sun, 30 Oct 2022 23:42:32 GMT",
"version": "v1"
},
{
"created": "Fri, 10 Feb 2023 00:11:08 GMT",
"version": "v2"
}
] |
2023-02-13
|
[
[
"Nakarachinda",
"Ratchaphat",
""
],
[
"Panpanich",
"Sirachak",
""
],
[
"Tsujikawa",
"Shinji",
""
],
[
"Wongjun",
"Pitayuth",
""
]
] |
In a model of spontaneous scalarization of neutron stars proposed by Damour and Esposite-Farese, a general relativistic branch becomes unstable to trigger tachyonic growth of a scalar field $\phi$ toward a scalarized branch. Applying this scenario to cosmology, there is fatal tachyonic instability of $\phi$ during inflation and matter dominance being incompatible with solar-system constraints on today's field value $\phi_0$. In the presence of a four-point coupling $g^2 \phi^2 \chi^2/2$ between $\phi$ and an inflaton field $\chi$, it was argued by Anson et al. that a positive mass squared heavier than the square of a Hubble expansion rate leads to the exponential suppression of $\phi$ during inflation and that $\phi_0$ can remain small even with the growth of $\phi$ after the radiation-dominated epoch. For several inflaton potentials approximated as $V(\chi)=m^2 \chi^2/2$ about the potential minimum, we study the dynamics of $\phi$ during reheating as well as other cosmological epochs in detail. For certain ranges of the coupling $g$, the homogeneous field $\phi$ can be amplified by parametric resonance during a coherent oscillation of the inflaton. Incorporating the backreaction of created particles under a Hartree approximation, the maximum values of $\phi$ reached during preheating are significantly smaller than those obtained without the backreaction. We also find that the minimum values of $g$ consistent with solar system bounds on $\phi$ at the end of reheating are of order $10^{-5}$ and hence there is a wide range of acceptable values of $g$. Thus, the scenario proposed by Anson et al. naturally leads to the viable cosmological evolution of $\phi$ consistent with local gravity constraints, without modifying the property of scalarized neutron stars.
|
2312.12393
|
Adam Zenon Kaczmarek
|
Adam Z. Kaczmarek and Dominik Szcz\k{e}\'sniak
|
The hybrid cosmology in the scalar-tensor representation of
$f(\mathcal{G},T)$ gravity
|
14 pages, 4 figures
| null | null | null |
gr-qc
|
http://creativecommons.org/licenses/by/4.0/
|
In this work, the $f(\mathcal{G},T)$ theory of gravity is recast in terms of
the $\phi$ and $\psi$ fields within the scalar-tensor formulation, where
$\mathcal{G}$ is the Gauss-Bonnet term and $T$ denotes the trace of the
energy-momentum tensor. The general aspects of the introduced reformulation are
discussed and the reconstruction of the cosmological scenarios is presented,
focusing on the so-called hybrid evolution. As a result, the scalar-tensor
$f(\mathcal{G},T)$ theory is successfully reconstructed for the early and late
time approximations with the corresponding potentials. The procedure of
recovering the $f(\mathcal{G},T)$ theory in the original formulation is
performed for the late time evolution and a specific quadratic potential. The
scalar-tensor formulation introduced herein not only facilitates the
description of various cosmic phases but also serves as a viable alternative
portrayal of the $f(\mathcal{G},T)$ gravity which can be viewed as an extension
of the well-established scalar Einstein-Gauss-Bonnet gravity.
|
[
{
"created": "Tue, 19 Dec 2023 18:31:13 GMT",
"version": "v1"
}
] |
2023-12-20
|
[
[
"Kaczmarek",
"Adam Z.",
""
],
[
"Szczęśniak",
"Dominik",
""
]
] |
In this work, the $f(\mathcal{G},T)$ theory of gravity is recast in terms of the $\phi$ and $\psi$ fields within the scalar-tensor formulation, where $\mathcal{G}$ is the Gauss-Bonnet term and $T$ denotes the trace of the energy-momentum tensor. The general aspects of the introduced reformulation are discussed and the reconstruction of the cosmological scenarios is presented, focusing on the so-called hybrid evolution. As a result, the scalar-tensor $f(\mathcal{G},T)$ theory is successfully reconstructed for the early and late time approximations with the corresponding potentials. The procedure of recovering the $f(\mathcal{G},T)$ theory in the original formulation is performed for the late time evolution and a specific quadratic potential. The scalar-tensor formulation introduced herein not only facilitates the description of various cosmic phases but also serves as a viable alternative portrayal of the $f(\mathcal{G},T)$ gravity which can be viewed as an extension of the well-established scalar Einstein-Gauss-Bonnet gravity.
|
1807.10243
|
Cosimo Bambi
|
Yerong Xu, Sourabh Nampalliwar, Askar B. Abdikamalov, Dimitry
Ayzenberg, Cosimo Bambi, Thomas Dauser, Javier A. Garcia, Jiachen Jiang
|
A study of the strong gravity region of the black hole in GS 1354-645
|
6 pages, 3 figures. v2: refereed version
|
Astrophys.J. 865: 134 (2018)
|
10.3847/1538-4357/aadb9d
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is thought that the spacetime metric around astrophysical black holes is
well described by the Kerr solution of Einstein's gravity. However, a robust
observational evidence of the Kerr nature of these objects is still lacking.
Here we fit the X-ray spectrum of the stellar-mass black hole in GS 1354-645
with a disk reflection model beyond Einstein's gravity in order test the Kerr
black hole hypothesis. We consider the Johannsen metric with the deformation
parameters $\alpha_{13}$ and $\alpha_{22}$. The Kerr metric is recovered for
$\alpha_{13} = \alpha_{22} = 0$. For $\alpha_{22} = 0$, our measurements of the
black hole spin and of the deformation parameter $\alpha_{13}$ are $a_* >
0.975$ and $-0.34 < \alpha_{13} < 0.16$, respectively. For $\alpha_{13} = 0$,
we find $a_* > 0.975$ and $-0.09 < \alpha_{22} < 0.42$. All the reported
uncertainties are at 99% of confidence level for two relevant parameters.
|
[
{
"created": "Thu, 26 Jul 2018 17:05:02 GMT",
"version": "v1"
},
{
"created": "Mon, 1 Oct 2018 13:07:48 GMT",
"version": "v2"
}
] |
2018-10-02
|
[
[
"Xu",
"Yerong",
""
],
[
"Nampalliwar",
"Sourabh",
""
],
[
"Abdikamalov",
"Askar B.",
""
],
[
"Ayzenberg",
"Dimitry",
""
],
[
"Bambi",
"Cosimo",
""
],
[
"Dauser",
"Thomas",
""
],
[
"Garcia",
"Javier A.",
""
],
[
"Jiang",
"Jiachen",
""
]
] |
It is thought that the spacetime metric around astrophysical black holes is well described by the Kerr solution of Einstein's gravity. However, a robust observational evidence of the Kerr nature of these objects is still lacking. Here we fit the X-ray spectrum of the stellar-mass black hole in GS 1354-645 with a disk reflection model beyond Einstein's gravity in order test the Kerr black hole hypothesis. We consider the Johannsen metric with the deformation parameters $\alpha_{13}$ and $\alpha_{22}$. The Kerr metric is recovered for $\alpha_{13} = \alpha_{22} = 0$. For $\alpha_{22} = 0$, our measurements of the black hole spin and of the deformation parameter $\alpha_{13}$ are $a_* > 0.975$ and $-0.34 < \alpha_{13} < 0.16$, respectively. For $\alpha_{13} = 0$, we find $a_* > 0.975$ and $-0.09 < \alpha_{22} < 0.42$. All the reported uncertainties are at 99% of confidence level for two relevant parameters.
|
1310.1412
|
M Blagojevi\'c
|
M. Blagojevi\'c, B. Cvetkovi\'c, and M. Vasili\'c
|
"Exotic" black holes with torsion
|
Revtex4, 3 pages
|
Phys.Rev. D88 (2013) 101501(R)
|
10.1103/PhysRevD.88.101501
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the context of three-dimensional gravity with torsion, the concepts of
standard and "exotic" Banados-Teitelboim-Zanelli black holes are generalized by
going over to black holes with torsion. This approach provides a unified
insight into thermodynamics of black holes, with or without torsion.
|
[
{
"created": "Fri, 4 Oct 2013 21:27:16 GMT",
"version": "v1"
}
] |
2013-12-06
|
[
[
"Blagojević",
"M.",
""
],
[
"Cvetković",
"B.",
""
],
[
"Vasilić",
"M.",
""
]
] |
In the context of three-dimensional gravity with torsion, the concepts of standard and "exotic" Banados-Teitelboim-Zanelli black holes are generalized by going over to black holes with torsion. This approach provides a unified insight into thermodynamics of black holes, with or without torsion.
|
1711.01394
|
Chopin Soo
|
Eyo Eyo Ita III, Chopin Soo and Hoi-Lai Yu
|
Cosmic time and reduced phase space of General Relativity
|
8 pages, replaced by published version
|
Phys. Rev. D 97, 104021 (2018)
|
10.1103/PhysRevD.97.104021
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In an ever-expanding spatially closed universe, the fractional change of the
volume is the preeminent intrinsic time interval to describe evolution in
General Relativity. The expansion of the universe serves as a subsidiary
condition which transforms Einstein's theory from a first class to a second
class constrained system when the physical degrees of freedom (d.o.f.) are
identified with transverse traceless excitations. The super-Hamiltonian
constraint is solved by eliminating the trace of the momentum in terms of the
other variables, and spatial diffeomorphism symmetry is tackled explicitly by
imposing transversality. The theorems of Maskawa-Nishijima appositely relate
the reduced phase space to the physical variables in canonical functional
integral and Dirac's criterion for second class constraints to nonvanishing
Faddeev-Popov determinants in the phase space measures. A reduced physical
Hamiltonian for intrinsic time evolution of the two physical d.o.f. emerges.
Freed from the first class Dirac algebra, deformation of the Hamiltonian
constraint is permitted, and natural extension of the Hamiltonian while
maintaining spatial diffeomorphism invariance leads to a theory with
Cotton-York term as the ultraviolet completion of Einstein's theory.
|
[
{
"created": "Sat, 4 Nov 2017 04:53:12 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Jun 2018 09:02:21 GMT",
"version": "v2"
}
] |
2018-06-14
|
[
[
"Ita",
"Eyo Eyo",
"III"
],
[
"Soo",
"Chopin",
""
],
[
"Yu",
"Hoi-Lai",
""
]
] |
In an ever-expanding spatially closed universe, the fractional change of the volume is the preeminent intrinsic time interval to describe evolution in General Relativity. The expansion of the universe serves as a subsidiary condition which transforms Einstein's theory from a first class to a second class constrained system when the physical degrees of freedom (d.o.f.) are identified with transverse traceless excitations. The super-Hamiltonian constraint is solved by eliminating the trace of the momentum in terms of the other variables, and spatial diffeomorphism symmetry is tackled explicitly by imposing transversality. The theorems of Maskawa-Nishijima appositely relate the reduced phase space to the physical variables in canonical functional integral and Dirac's criterion for second class constraints to nonvanishing Faddeev-Popov determinants in the phase space measures. A reduced physical Hamiltonian for intrinsic time evolution of the two physical d.o.f. emerges. Freed from the first class Dirac algebra, deformation of the Hamiltonian constraint is permitted, and natural extension of the Hamiltonian while maintaining spatial diffeomorphism invariance leads to a theory with Cotton-York term as the ultraviolet completion of Einstein's theory.
|
1804.03158
|
Fethi M. Ramazanoglu
|
Fethi M Ramazano\u{g}lu
|
Spontaneous growth of gauge fields in gravity through the Higgs
mechanism
|
This version corrects some equations which were also updated in the
online version at PRD. Conclusions are unchanged
|
Phys. Rev. D 98, 044013 (2018)
|
10.1103/PhysRevD.98.044013
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We introduce gravity theories featuring spontaneously growing gauge fields
where the growth is due to the Higgs mechanism. The underlying physics is
inspired by the spontaneous scalarization phenomena in scalar-tensor theories.
The tachyonic instability that causes the growth in spontaneous scalarization
and its analog for vector fields is introduced not as an explicit potential
term, but through a scalar coupling using a Higgs field. The resulting theories
are distinct from previous examples of spontaneous tensorization in that they
respect the gauge symmetry at the level of the action. Our results are valid
for both Abelian and non-Abelian gauge theories, and this is the first study of
the spontaneous growth of the latter. We discuss astrophysical implications of
these theories and argue their relevance especially in the strong gravity
regime.
|
[
{
"created": "Mon, 9 Apr 2018 18:00:16 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Aug 2018 12:39:10 GMT",
"version": "v2"
},
{
"created": "Mon, 7 Oct 2019 14:22:29 GMT",
"version": "v3"
}
] |
2019-10-08
|
[
[
"Ramazanoğlu",
"Fethi M",
""
]
] |
We introduce gravity theories featuring spontaneously growing gauge fields where the growth is due to the Higgs mechanism. The underlying physics is inspired by the spontaneous scalarization phenomena in scalar-tensor theories. The tachyonic instability that causes the growth in spontaneous scalarization and its analog for vector fields is introduced not as an explicit potential term, but through a scalar coupling using a Higgs field. The resulting theories are distinct from previous examples of spontaneous tensorization in that they respect the gauge symmetry at the level of the action. Our results are valid for both Abelian and non-Abelian gauge theories, and this is the first study of the spontaneous growth of the latter. We discuss astrophysical implications of these theories and argue their relevance especially in the strong gravity regime.
|
1606.04359
|
Emmanuil Saridakis
|
Rafael C. Nunes, Supriya Pan, Emmanuel N. Saridakis
|
New observational constraints on f(T) gravity from cosmic chronometers
|
24 pages, 9 Figures, 7 Tables, version published in JCAP
|
JCAP 1608 (2016) no.08, 011
|
10.1088/1475-7516/2016/08/011
| null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We use the local value of the Hubble constant recently measured with 2.4%
precision, as well as the latest compilation of cosmic chronometers data,
together with standard probes such as Supernovae Type Ia and Baryon Acoustic
Oscillation distance measurements, in order to impose constraints on the viable
and most used f(T) gravity models, where T is the torsion scalar in
teleparallel gravity. In particular, we consider three f(T) models with two
parameters, out of which one is independent, and we quantify their deviation
from $\Lambda$CDM cosmology through a sole parameter. Our analysis reveals that
for one of the models a small but non-zero deviation from $\Lambda$CDM
cosmology is slightly favored, while for the other models the best fit is very
close to $\Lambda$CDM scenario. Clearly, f(T) gravity is consistent with
observations, and it can serve as a candidate for modified gravity.
|
[
{
"created": "Tue, 7 Jun 2016 19:18:29 GMT",
"version": "v1"
},
{
"created": "Tue, 9 Aug 2016 08:06:40 GMT",
"version": "v2"
}
] |
2016-08-10
|
[
[
"Nunes",
"Rafael C.",
""
],
[
"Pan",
"Supriya",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] |
We use the local value of the Hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as Supernovae Type Ia and Baryon Acoustic Oscillation distance measurements, in order to impose constraints on the viable and most used f(T) gravity models, where T is the torsion scalar in teleparallel gravity. In particular, we consider three f(T) models with two parameters, out of which one is independent, and we quantify their deviation from $\Lambda$CDM cosmology through a sole parameter. Our analysis reveals that for one of the models a small but non-zero deviation from $\Lambda$CDM cosmology is slightly favored, while for the other models the best fit is very close to $\Lambda$CDM scenario. Clearly, f(T) gravity is consistent with observations, and it can serve as a candidate for modified gravity.
|
gr-qc/9508013
| null |
S. Mignemi
|
Exact solutions, symmetries and quantization of two-dimensional
higher-derivative gravity with dynamical torsion
|
10 pages, plain Tex, 3 figures available from the author
| null | null |
IRS-9502
|
gr-qc
| null |
We investigate two-dimensional higher derivative gravitational theories in a
Riemann-Cartan framework and obtain the most general static black hole
solutions in conformal coordinates. We also consider the hamiltonian
formulation of the theory and discuss its symmetries, showing they are
implemented by a non-linear generalizations of the 2-dimensional Poincar\'e
algebra. Finally, we discuss the quantization in the Dirac formalism.
|
[
{
"created": "Sat, 5 Aug 1995 14:30:54 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Mignemi",
"S.",
""
]
] |
We investigate two-dimensional higher derivative gravitational theories in a Riemann-Cartan framework and obtain the most general static black hole solutions in conformal coordinates. We also consider the hamiltonian formulation of the theory and discuss its symmetries, showing they are implemented by a non-linear generalizations of the 2-dimensional Poincar\'e algebra. Finally, we discuss the quantization in the Dirac formalism.
|
0803.0648
|
Istv\'an R\'acz
|
Istv\'an R\'acz
|
Space-time extensions II
|
42 pages, no figures, small changes to match the published version
|
Class.Quant.Grav.27:155007,2010
|
10.1088/0264-9381/27/15/155007
| null |
gr-qc math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The global extendibility of smooth causal geodesically incomplete spacetimes
is investigated. Denote by $\gamma$ one of the incomplete non-extendible causal
geodesics of a causal geodesically incomplete spacetime $(M,g_{ab})$. First, it
is shown that it is always possible to select a synchronised family of causal
geodesics $\Gamma$ and an open neighbourhood $\mathcal{U}$ of a final segment
of $\gamma$ in $M$ such that $\mathcal{U}$ is comprised by members of $\Gamma$,
and suitable local coordinates can be defined everywhere on $\mathcal{U}$
provided that $\gamma$ does not terminate either on a tidal force tensor
singularity or on a topological singularity. It is also shown that if, in
addition, the spacetime, $(M,g_{ab})$, is globally hyperbolic, and the
components of the curvature tensor, and its covariant derivatives up to order
$k-1$ are bounded on $\mathcal{U}$, and also the line integrals of the
components of the $k^{th}$-order covariant derivatives are finite along the
members of $\Gamma$---where all the components are meant to be registered with
respect to a synchronised frame field on $\mathcal{U}$---then there exists a
$C^{k-}$ extension $\Phi: (M,g_{ab}) \rightarrow
(\widehat{M},\widehat{g}_{ab})$ so that for each $\bar\gamma\in\Gamma$, which
is inextendible in $(M,g_{ab})$, the image, $\Phi\circ\bar\gamma$, is
extendible in $(\widehat{M},\widehat{g}_{ab})$. Finally, it is also proved that
whenever $\gamma$ does terminate on a topological singularity $(M,g_{ab})$
cannot be generic.
|
[
{
"created": "Wed, 5 Mar 2008 12:55:12 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jun 2010 22:02:23 GMT",
"version": "v2"
}
] |
2010-06-29
|
[
[
"Rácz",
"István",
""
]
] |
The global extendibility of smooth causal geodesically incomplete spacetimes is investigated. Denote by $\gamma$ one of the incomplete non-extendible causal geodesics of a causal geodesically incomplete spacetime $(M,g_{ab})$. First, it is shown that it is always possible to select a synchronised family of causal geodesics $\Gamma$ and an open neighbourhood $\mathcal{U}$ of a final segment of $\gamma$ in $M$ such that $\mathcal{U}$ is comprised by members of $\Gamma$, and suitable local coordinates can be defined everywhere on $\mathcal{U}$ provided that $\gamma$ does not terminate either on a tidal force tensor singularity or on a topological singularity. It is also shown that if, in addition, the spacetime, $(M,g_{ab})$, is globally hyperbolic, and the components of the curvature tensor, and its covariant derivatives up to order $k-1$ are bounded on $\mathcal{U}$, and also the line integrals of the components of the $k^{th}$-order covariant derivatives are finite along the members of $\Gamma$---where all the components are meant to be registered with respect to a synchronised frame field on $\mathcal{U}$---then there exists a $C^{k-}$ extension $\Phi: (M,g_{ab}) \rightarrow (\widehat{M},\widehat{g}_{ab})$ so that for each $\bar\gamma\in\Gamma$, which is inextendible in $(M,g_{ab})$, the image, $\Phi\circ\bar\gamma$, is extendible in $(\widehat{M},\widehat{g}_{ab})$. Finally, it is also proved that whenever $\gamma$ does terminate on a topological singularity $(M,g_{ab})$ cannot be generic.
|
gr-qc/9910099
|
Chris Doran
|
Chris Doran
|
A new form of the Kerr solution
|
8 pages, LaTeX, no figures. Corrected and improved version. To appear
in Phys. Rev. D
|
Phys.Rev. D61 (2000) 067503
|
10.1103/PhysRevD.61.067503
| null |
gr-qc astro-ph
| null |
A new form of the Kerr solution is presented. The solution involves a time
coordinate which represents the local proper time for free-falling observers on
a set of simple trajectories. Many physical phenomena are particularly clear
when related to this time coordinate. The chosen coordinates also ensure that
the solution is well behaved at the horizon. The solution is well suited to the
tetrad formalism and a convenient null tetrad is presented. The Dirac
Hamiltonian in a Kerr background is also given and, for one choice of tetrad,
it takes on a simple, Hermitian form.
|
[
{
"created": "Wed, 27 Oct 1999 10:49:50 GMT",
"version": "v1"
},
{
"created": "Fri, 29 Oct 1999 08:11:00 GMT",
"version": "v2"
},
{
"created": "Mon, 31 Jan 2000 09:23:11 GMT",
"version": "v3"
}
] |
2009-10-31
|
[
[
"Doran",
"Chris",
""
]
] |
A new form of the Kerr solution is presented. The solution involves a time coordinate which represents the local proper time for free-falling observers on a set of simple trajectories. Many physical phenomena are particularly clear when related to this time coordinate. The chosen coordinates also ensure that the solution is well behaved at the horizon. The solution is well suited to the tetrad formalism and a convenient null tetrad is presented. The Dirac Hamiltonian in a Kerr background is also given and, for one choice of tetrad, it takes on a simple, Hermitian form.
|
1511.02060
|
Juan Calderon Bustillo
|
Juan Calder\'on Bustillo, Sascha Husa, Alicia M. Sintes and Michael
P\"urrer
|
Impact of gravitational radiation higher order modes on single
aligned-spin gravitational wave searches for binary black holes
|
11 pages, 10 figures
|
Phys. Rev. D 93, 084019 (2016)
|
10.1103/PhysRevD.93.084019
|
LIGO-P1500184
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Current template-based gravitational wave searches for compact binary
coalescences (CBC) use waveform models that neglect the higher order modes
content of the gravitational radiation emitted, considering only the
quadrupolar $(\ell,|m|)=(2,2)$ modes. We study the effect of such a neglection
for the case of aligned-spin CBC searches for equal-spin (and non-spinning)
binary black holes in the context of two versions of Advanced LIGO: the
upcoming 2015 version, known as early Advanced LIGO (eaLIGO) and its
Zero-Detuned High Energy Power version, that we will refer to as Advanced LIGO
(AdvLIGO). In addition, we study the case of a non-spinning search for initial
LIGO (iLIGO). We do this via computing the effectualness of the aligned-spin
SEOBNRv1 ROM waveform family, which only considers quadrupolar modes, towards
hybrid post-Newtonian/Numerical Relativity waveforms which contain higher order
modes. We find that for all LIGO versions, losses of more than $10\%$ of events
occur for mass ratio $q\geq6$ and $M \geq 100M_\odot$ due to the neglection of
higher modes. Moreover, for iLIGO and eaLIGO, losses notably increase up to
$(39,23)\%$ respectively for the highest mass $(220M_\odot)$ and mass ratio
($q=8$) studied. For the case of early AdvLIGO, losses of $10\%$ occur for
$M>50M_\odot$ and $q\geq6$. Neglection of higher modes leads to
observation-averaged systematic parameter biases towards lower spin, total mass
and chirp mass. For completeness, we perform a preliminar, non-exhaustive
comparison of systematic biases to statistical errors. We find that, for a
given SNR, systematic biases dominate over statistical errors at much lower
total mass for eaLIGO than for AdvLIGO.
|
[
{
"created": "Fri, 6 Nov 2015 13:02:33 GMT",
"version": "v1"
},
{
"created": "Fri, 13 Nov 2015 12:27:41 GMT",
"version": "v2"
}
] |
2016-04-20
|
[
[
"Bustillo",
"Juan Calderón",
""
],
[
"Husa",
"Sascha",
""
],
[
"Sintes",
"Alicia M.",
""
],
[
"Pürrer",
"Michael",
""
]
] |
Current template-based gravitational wave searches for compact binary coalescences (CBC) use waveform models that neglect the higher order modes content of the gravitational radiation emitted, considering only the quadrupolar $(\ell,|m|)=(2,2)$ modes. We study the effect of such a neglection for the case of aligned-spin CBC searches for equal-spin (and non-spinning) binary black holes in the context of two versions of Advanced LIGO: the upcoming 2015 version, known as early Advanced LIGO (eaLIGO) and its Zero-Detuned High Energy Power version, that we will refer to as Advanced LIGO (AdvLIGO). In addition, we study the case of a non-spinning search for initial LIGO (iLIGO). We do this via computing the effectualness of the aligned-spin SEOBNRv1 ROM waveform family, which only considers quadrupolar modes, towards hybrid post-Newtonian/Numerical Relativity waveforms which contain higher order modes. We find that for all LIGO versions, losses of more than $10\%$ of events occur for mass ratio $q\geq6$ and $M \geq 100M_\odot$ due to the neglection of higher modes. Moreover, for iLIGO and eaLIGO, losses notably increase up to $(39,23)\%$ respectively for the highest mass $(220M_\odot)$ and mass ratio ($q=8$) studied. For the case of early AdvLIGO, losses of $10\%$ occur for $M>50M_\odot$ and $q\geq6$. Neglection of higher modes leads to observation-averaged systematic parameter biases towards lower spin, total mass and chirp mass. For completeness, we perform a preliminar, non-exhaustive comparison of systematic biases to statistical errors. We find that, for a given SNR, systematic biases dominate over statistical errors at much lower total mass for eaLIGO than for AdvLIGO.
|
1608.05020
|
Yurii Ignat'ev
|
Yurii Ignat'ev, Alexander Agathonov and Dmitry Ignatyev
|
Statistical Cosmological Fermion Systems With Interparticle Fantom
Scalar Interaction
|
67 pages, 71 figures, 43 references
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The article represents a research of the cosmological evolution of fermion
statistical systems with fantom scalar interaction where "kinetic" term's
contribution to the total energy of a scalar field is negative. As a result of
analytical and numerical simulation of such systems it has been revealed a
existence of four possible scenarios depending on parameters of the system and
initial conditions. Among these scenarios there are scenarios with an early,
intermediate and late non-relativistic stages of the cosmological evolution,
all of which also have necessary inflation stage.
|
[
{
"created": "Wed, 17 Aug 2016 17:07:25 GMT",
"version": "v1"
}
] |
2016-08-18
|
[
[
"Ignat'ev",
"Yurii",
""
],
[
"Agathonov",
"Alexander",
""
],
[
"Ignatyev",
"Dmitry",
""
]
] |
The article represents a research of the cosmological evolution of fermion statistical systems with fantom scalar interaction where "kinetic" term's contribution to the total energy of a scalar field is negative. As a result of analytical and numerical simulation of such systems it has been revealed a existence of four possible scenarios depending on parameters of the system and initial conditions. Among these scenarios there are scenarios with an early, intermediate and late non-relativistic stages of the cosmological evolution, all of which also have necessary inflation stage.
|
2104.05756
|
Jakub Bilski
|
Jakub Bilski
|
Relativistic classical theory II. Holonomy-flux representation of
gravitational degrees of freedom
|
42 pages, 13 figures
| null | null | null |
gr-qc hep-lat hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This article describes the regularization of the generally relativistic gauge
field representation of gravity on a piecewise linear lattice. It is a part of
the program concerning the classical relativistic theory of fundamental
interactions, represented by minimally coupled gauge vector field densities and
half-densities. The correspondence between the local Darboux coordinates on
phase space and the local structure of the links of the lattice, embedded in
the spatial manifold, is demonstrated. Thus, the canonical coordinates are
replaceable by links-related quantities. This idea and the significant part of
formalism are directly based on the model of canonical loop quantum gravity
(CLQG).
The first stage of this program is formulated regarding the gauge field,
which dynamics is independent of other fundamental fields, but contributes to
their dynamics. This gauge field, which determines systems equivalence in the
actions defining all fundamental interactions, represents Einsteinian gravity.
The related links-defined quantities depend on holonomies of gravitational
connections and fluxes of densitized dreibeins. This article demonstrates how
to determine these quantities, which lead to a nonpertubative formalism that
preserves the general postulate of relativity. From this perspective, the
formalism presented in this article is analogous to the Ashtekar-Barbero-Holst
formulation on which CLQG is based. However, in this project, it is
additionally required that the fields' coordinates are quantizable in the
standard canonical procedure for a gauge theory and that any approximation in
the construction of the model is at least as precisely demonstrated as the
gauge invariance. These requirements lead to new relations between holonomies
and connections, and the representation of the densitized deibein determinant
that is more precise than the volume representation in CLQG.
|
[
{
"created": "Mon, 12 Apr 2021 18:37:34 GMT",
"version": "v1"
}
] |
2021-04-14
|
[
[
"Bilski",
"Jakub",
""
]
] |
This article describes the regularization of the generally relativistic gauge field representation of gravity on a piecewise linear lattice. It is a part of the program concerning the classical relativistic theory of fundamental interactions, represented by minimally coupled gauge vector field densities and half-densities. The correspondence between the local Darboux coordinates on phase space and the local structure of the links of the lattice, embedded in the spatial manifold, is demonstrated. Thus, the canonical coordinates are replaceable by links-related quantities. This idea and the significant part of formalism are directly based on the model of canonical loop quantum gravity (CLQG). The first stage of this program is formulated regarding the gauge field, which dynamics is independent of other fundamental fields, but contributes to their dynamics. This gauge field, which determines systems equivalence in the actions defining all fundamental interactions, represents Einsteinian gravity. The related links-defined quantities depend on holonomies of gravitational connections and fluxes of densitized dreibeins. This article demonstrates how to determine these quantities, which lead to a nonpertubative formalism that preserves the general postulate of relativity. From this perspective, the formalism presented in this article is analogous to the Ashtekar-Barbero-Holst formulation on which CLQG is based. However, in this project, it is additionally required that the fields' coordinates are quantizable in the standard canonical procedure for a gauge theory and that any approximation in the construction of the model is at least as precisely demonstrated as the gauge invariance. These requirements lead to new relations between holonomies and connections, and the representation of the densitized deibein determinant that is more precise than the volume representation in CLQG.
|
gr-qc/0206035
|
Lee Lindblom
|
Lee Lindblom and Mark A. Scheel
|
Energy Norms and the Stability of the Einstein Evolution Equations
|
Corrected typos; to appear in Physical Review D
|
Phys.Rev. D66 (2002) 084014
|
10.1103/PhysRevD.66.084014
| null |
gr-qc
| null |
The Einstein evolution equations may be written in a variety of equivalent
analytical forms, but numerical solutions of these different formulations
display a wide range of growth rates for constraint violations. For symmetric
hyperbolic formulations of the equations, an exact expression for the growth
rate is derived using an energy norm. This expression agrees with the growth
rate determined by numerical solution of the equations. An approximate method
for estimating the growth rate is also derived. This estimate can be evaluated
algebraically from the initial data, and is shown to exhibit qualitatively the
same dependence as the numerically-determined rate on the parameters that
specify the formulation of the equations. This simple rate estimate therefore
provides a useful tool for finding the most well-behaved forms of the evolution
equations.
|
[
{
"created": "Wed, 12 Jun 2002 19:39:45 GMT",
"version": "v1"
},
{
"created": "Mon, 19 Aug 2002 20:35:43 GMT",
"version": "v2"
},
{
"created": "Fri, 27 Sep 2002 18:15:52 GMT",
"version": "v3"
}
] |
2009-11-07
|
[
[
"Lindblom",
"Lee",
""
],
[
"Scheel",
"Mark A.",
""
]
] |
The Einstein evolution equations may be written in a variety of equivalent analytical forms, but numerical solutions of these different formulations display a wide range of growth rates for constraint violations. For symmetric hyperbolic formulations of the equations, an exact expression for the growth rate is derived using an energy norm. This expression agrees with the growth rate determined by numerical solution of the equations. An approximate method for estimating the growth rate is also derived. This estimate can be evaluated algebraically from the initial data, and is shown to exhibit qualitatively the same dependence as the numerically-determined rate on the parameters that specify the formulation of the equations. This simple rate estimate therefore provides a useful tool for finding the most well-behaved forms of the evolution equations.
|
2307.13435
|
Nelson V Nunes
|
N. V. Nunes, N. Bartel, A. Belonenko, G. D. Manucharyan, S. M. Popov,
V. N. Rudenko, L. I. Gurvits, G. Cim\`o, G. Molera Calv\'es, M. V.
Zakhvatkin, M. F. Bietenholz
|
Gravitational redshift test of EEP with RA from near Earth to the
distance of the Moon
|
Nelson V Nunes et al 2023 Class. Quantum Grav. in press
https://doi.org/10.1088/1361-6382/ace609
| null |
10.1088/1361-6382/ace609
| null |
gr-qc astro-ph.IM
|
http://creativecommons.org/licenses/by/4.0/
|
The Einstein Equivalence Principle (EEP) is a cornerstone of general
relativity and predicts the existence of gravitational redshift. We report on
new results of measuring this shift with RadioAstron (RA), a space VLBI
spacecraft launched into an evolving high eccentricity orbit around Earth with
geocentric distances reaching 353,000 km. The spacecraft and ground tracking
stations at Pushchino, Russia, and Green Bank, USA, were each equipped with a
hydrogen maser frequency standard allowing a possible violation of the
predicted gravitational redshift, in the form of a violation parameter
$\varepsilon$, to be measured. By alternating between RadioAstron's frequency
referencing modes during dedicated sessions between 2015 and 2017, the recorded
downlink frequencies can essentially be corrected for the non-relativistic
Doppler shift. We report on an analysis using the Doppler-tracking frequency
measurements made during these sessions and find $\varepsilon = (2.1 \pm
3.3)\times10^{-4}$. We also discuss prospects for measuring $\varepsilon$ with
a significantly smaller uncertainty using instead the time-domain recordings of
the spacecraft signals and envision how $10^{-7}$ might be possible for a
future space VLBI mission.
|
[
{
"created": "Tue, 25 Jul 2023 12:02:36 GMT",
"version": "v1"
}
] |
2023-07-26
|
[
[
"Nunes",
"N. V.",
""
],
[
"Bartel",
"N.",
""
],
[
"Belonenko",
"A.",
""
],
[
"Manucharyan",
"G. D.",
""
],
[
"Popov",
"S. M.",
""
],
[
"Rudenko",
"V. N.",
""
],
[
"Gurvits",
"L. I.",
""
],
[
"Cimò",
"G.",
""
],
[
"Calvés",
"G. Molera",
""
],
[
"Zakhvatkin",
"M. V.",
""
],
[
"Bietenholz",
"M. F.",
""
]
] |
The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space VLBI spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric distances reaching 353,000 km. The spacecraft and ground tracking stations at Pushchino, Russia, and Green Bank, USA, were each equipped with a hydrogen maser frequency standard allowing a possible violation of the predicted gravitational redshift, in the form of a violation parameter $\varepsilon$, to be measured. By alternating between RadioAstron's frequency referencing modes during dedicated sessions between 2015 and 2017, the recorded downlink frequencies can essentially be corrected for the non-relativistic Doppler shift. We report on an analysis using the Doppler-tracking frequency measurements made during these sessions and find $\varepsilon = (2.1 \pm 3.3)\times10^{-4}$. We also discuss prospects for measuring $\varepsilon$ with a significantly smaller uncertainty using instead the time-domain recordings of the spacecraft signals and envision how $10^{-7}$ might be possible for a future space VLBI mission.
|
1912.08089
|
Ester Piedipalumbo
|
Ester Piedipalumbo, Mariafelicia De Laurentis, Salvatore Capozziello
|
Noether symmetries in Interacting Quintessence Cosmology
|
21 pages, 9 figures, accepted for publication in Physics of the Dark
Universe
| null | null | null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The Noether Symmetry Approach is applied to interacting quintessence
cosmology with the aim to search for exact solutions and select scalar-field
self-interaction potentials. It turns out that the solutions found are
compatible with the accelerated expansion of the Universe and with
observational dataset, as the SNeIa
Pantheon data.
|
[
{
"created": "Mon, 16 Dec 2019 17:14:19 GMT",
"version": "v1"
}
] |
2019-12-19
|
[
[
"Piedipalumbo",
"Ester",
""
],
[
"De Laurentis",
"Mariafelicia",
""
],
[
"Capozziello",
"Salvatore",
""
]
] |
The Noether Symmetry Approach is applied to interacting quintessence cosmology with the aim to search for exact solutions and select scalar-field self-interaction potentials. It turns out that the solutions found are compatible with the accelerated expansion of the Universe and with observational dataset, as the SNeIa Pantheon data.
|
2102.05551
|
Genly Le\'on
|
Genly Leon, Esteban Gonz\'alez, Samuel Lepe, Claudio Michea and
Alfredo D. Millano
|
Averaging generalized scalar field cosmologies III: Kantowski--Sachs and
closed Friedmann--Lema\^itre--Robertson--Walker models
|
Research Program Averaging Generalized Scalar Field Cosmologies, part
III. 54 pages, 26 compound figures. Extended version
| null | null | null |
gr-qc math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Scalar field cosmologies with a generalized harmonic potential and matter
with energy density $\rho_m$, pressure $p_m$, and barotropic equation of state
(EoS) $p_m=(\gamma-1)\rho_m, \; \gamma\in[0,2]$ in Kantowski-Sachs (KS) and
closed Friedmann--Lema\^itre--Robertson--Walker (FLRW) metrics are
investigated. We use methods from non--linear dynamical systems theory and
averaging theory considering a time--dependent perturbation function $D$. We
define a regular dynamical system over a compact phase space, obtaining global
results. That is, for KS metric the global late--time attractors of full and
time--averaged systems are two anisotropic contracting solutions, which are
non--flat locally rotationally symmetric (LRS) Kasner and Taub (flat LRS
Kasner) for $0\leq \gamma \leq 2$, and flat FLRW matter--dominated universe if
$0\leq \gamma \leq \frac{2}{3}$. For closed FLRW metric late--time attractors
of full and averaged systems are a flat matter--dominated FLRW universe for
$0\leq \gamma \leq \frac{2}{3}$ as in KS and Einstein-de Sitter solution for
$0\leq\gamma<1$. Therefore, time--averaged system determines future asymptotics
of full system. Also, oscillations entering the system through Klein-Gordon
(KG) equation can be controlled and smoothed out when $D$ goes monotonically to
zero, and incidentally for the whole $D$-range for KS and for closed FLRW (if
$0\leq \gamma< 1$) too. However, for $\gamma\geq 1$ closed FLRW solutions of
the full system depart from the solutions of the averaged system as $D$ is
large. Our results are supported by numerical simulations.
|
[
{
"created": "Wed, 10 Feb 2021 16:34:52 GMT",
"version": "v1"
},
{
"created": "Fri, 12 Feb 2021 20:39:00 GMT",
"version": "v2"
},
{
"created": "Mon, 31 May 2021 22:20:03 GMT",
"version": "v3"
},
{
"created": "Thu, 5 Aug 2021 23:27:33 GMT",
"version": "v4"
}
] |
2021-08-09
|
[
[
"Leon",
"Genly",
""
],
[
"González",
"Esteban",
""
],
[
"Lepe",
"Samuel",
""
],
[
"Michea",
"Claudio",
""
],
[
"Millano",
"Alfredo D.",
""
]
] |
Scalar field cosmologies with a generalized harmonic potential and matter with energy density $\rho_m$, pressure $p_m$, and barotropic equation of state (EoS) $p_m=(\gamma-1)\rho_m, \; \gamma\in[0,2]$ in Kantowski-Sachs (KS) and closed Friedmann--Lema\^itre--Robertson--Walker (FLRW) metrics are investigated. We use methods from non--linear dynamical systems theory and averaging theory considering a time--dependent perturbation function $D$. We define a regular dynamical system over a compact phase space, obtaining global results. That is, for KS metric the global late--time attractors of full and time--averaged systems are two anisotropic contracting solutions, which are non--flat locally rotationally symmetric (LRS) Kasner and Taub (flat LRS Kasner) for $0\leq \gamma \leq 2$, and flat FLRW matter--dominated universe if $0\leq \gamma \leq \frac{2}{3}$. For closed FLRW metric late--time attractors of full and averaged systems are a flat matter--dominated FLRW universe for $0\leq \gamma \leq \frac{2}{3}$ as in KS and Einstein-de Sitter solution for $0\leq\gamma<1$. Therefore, time--averaged system determines future asymptotics of full system. Also, oscillations entering the system through Klein-Gordon (KG) equation can be controlled and smoothed out when $D$ goes monotonically to zero, and incidentally for the whole $D$-range for KS and for closed FLRW (if $0\leq \gamma< 1$) too. However, for $\gamma\geq 1$ closed FLRW solutions of the full system depart from the solutions of the averaged system as $D$ is large. Our results are supported by numerical simulations.
|
gr-qc/0601068
|
Mark D. Roberts
|
Mark D. Roberts
|
Quadratic field equations on the brane
|
To appear in Nuovo Cimento, updated to coincide with the published
version.
|
Nuovo Cim.B125:309-314,2010
|
10.1393/ncb/i2010-10873-7
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is shown that four dimensional vacuum Einstein solutions simply embedded
in five dimensions obey the Gauss-Bonnet-Einstein field equations:
$G_{ab}+\alpha GB_{ab}+\delta^{55}_{ab}\alpha\exp(-2\chi/\sqrt{\alpha})GB_4=0$
and the Pauli-Einstein equations $G_{ab}-3\alpha P_{ab}/5=0$, and the
Bach-Einstein equations $B_{ab}=0$. General equations are calculated for which
these and similar results follow. It is briefly argued that such field
equations could be significant on large distance scales.
|
[
{
"created": "Tue, 17 Jan 2006 14:25:49 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Mar 2010 16:07:22 GMT",
"version": "v2"
}
] |
2010-11-11
|
[
[
"Roberts",
"Mark D.",
""
]
] |
It is shown that four dimensional vacuum Einstein solutions simply embedded in five dimensions obey the Gauss-Bonnet-Einstein field equations: $G_{ab}+\alpha GB_{ab}+\delta^{55}_{ab}\alpha\exp(-2\chi/\sqrt{\alpha})GB_4=0$ and the Pauli-Einstein equations $G_{ab}-3\alpha P_{ab}/5=0$, and the Bach-Einstein equations $B_{ab}=0$. General equations are calculated for which these and similar results follow. It is briefly argued that such field equations could be significant on large distance scales.
|
gr-qc/0606114
|
Takashi Fukumoto
|
Takashi Fukumoto (1), Toshifumi Futamase (1), and Yousuke Itoh (2)
((1) Tohoku U., Japan, (2) U. of Wisconsin Milwaukee, USA)
|
On the Equation of Motion for a Fast Moving Small Object in the Strong
Field Point Particle Limit
|
accepted by Progress of Theoretical Physics
|
Prog.Theor.Phys. 116 (2006) 423-428
|
10.1143/PTP.116.423
| null |
gr-qc astro-ph
| null |
We give a straightforward and divergence free derivation of the equation of
motion for a small but finite object in an arbitrary background using strong
field point particle limit. The resulting equation becomes a generalized
geodesic for a non-rotating spherical object which is consisitent with previous
studies.
|
[
{
"created": "Tue, 27 Jun 2006 04:36:39 GMT",
"version": "v1"
},
{
"created": "Thu, 4 Jan 2007 08:02:23 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Fukumoto",
"Takashi",
"",
"Tohoku U., Japan"
],
[
"Futamase",
"Toshifumi",
"",
"Tohoku U., Japan"
],
[
"Itoh",
"Yousuke",
"",
"U. of Wisconsin Milwaukee, USA"
]
] |
We give a straightforward and divergence free derivation of the equation of motion for a small but finite object in an arbitrary background using strong field point particle limit. The resulting equation becomes a generalized geodesic for a non-rotating spherical object which is consisitent with previous studies.
|
gr-qc/0102097
|
Roman R. Zapatrin
|
A. Mallios, I. Raptis
|
Finitary Spacetime Sheaves of Quantum Causal Sets: Curving Quantum
Causality
|
This is a shortened version of the abstract. The paper is submitted
to the International Journal of Theoretical Physics
|
Int.J.Theor.Phys. 40 (2001) 1885-1928
| null | null |
gr-qc
| null |
A locally finite, causal and quantal substitute for a locally Minkowskian
principal fiber bundle $\cal{P}$ of modules of Cartan differential forms $\omg$
over a bounded region $X$ of a curved $C^{\infty}$-smooth differential manifold
spacetime $M$ with structure group ${\bf G}$ that of orthochronous Lorentz
transformations $L^{+}:=SO(1,3)^{\uparrow}$, is presented. ${\cal{P}}$ is the
structure on which classical Lorentzian gravity, regarded as a Yang-Mills type
of gauge theory of a $sl(2,\com)$-valued connection 1-form $\cal{A}$, is
usually formulated. The mathematical structure employed to model this
replacement of ${\cal{P}}$ is a principal finitary spacetime sheaf
$\vec{\cal{P}}_{n}$ of quantum causal sets $\amg_{n}$ with structure group
${\bf G}_{n}$, which is a finitary version of the group ${\bf G}$ of local
symmetries of General Relativity, and a finitary Lie algebra ${\bf
g}_{n}$-valued connection 1-form ${\cal{A}}_{n}$ on it, which is a section of
its sub-sheaf $\amg^{1}_{n}$. ${\cal{A}}_{n}$ is physically interpreted as the
dynamical field of a locally finite quantum causality, while its associated
curvature ${\cal{F}}_{n}$, as some sort of `finitary Lorentzian quantum
gravity.
|
[
{
"created": "Thu, 22 Feb 2001 13:21:58 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Mallios",
"A.",
""
],
[
"Raptis",
"I.",
""
]
] |
A locally finite, causal and quantal substitute for a locally Minkowskian principal fiber bundle $\cal{P}$ of modules of Cartan differential forms $\omg$ over a bounded region $X$ of a curved $C^{\infty}$-smooth differential manifold spacetime $M$ with structure group ${\bf G}$ that of orthochronous Lorentz transformations $L^{+}:=SO(1,3)^{\uparrow}$, is presented. ${\cal{P}}$ is the structure on which classical Lorentzian gravity, regarded as a Yang-Mills type of gauge theory of a $sl(2,\com)$-valued connection 1-form $\cal{A}$, is usually formulated. The mathematical structure employed to model this replacement of ${\cal{P}}$ is a principal finitary spacetime sheaf $\vec{\cal{P}}_{n}$ of quantum causal sets $\amg_{n}$ with structure group ${\bf G}_{n}$, which is a finitary version of the group ${\bf G}$ of local symmetries of General Relativity, and a finitary Lie algebra ${\bf g}_{n}$-valued connection 1-form ${\cal{A}}_{n}$ on it, which is a section of its sub-sheaf $\amg^{1}_{n}$. ${\cal{A}}_{n}$ is physically interpreted as the dynamical field of a locally finite quantum causality, while its associated curvature ${\cal{F}}_{n}$, as some sort of `finitary Lorentzian quantum gravity.
|
0801.2639
|
Manfred Requardt
|
Manfred Requardt
|
Thermodynamics meets Special Relativity -- or what is real in Physics?
|
27 pages, latex, no figures
| null | null | null |
gr-qc cond-mat.stat-mech hep-th
| null |
In this paper we carefully reexamine the various framworks existing in the
field of relativistic thermodynamics. We scrutinize in particular the different
conceptual foundations of notions like the relativistic work, heat force,
moving heat and relativistic temperature. As to the latter notion we argue
that, as in ordinary thermodynamics, relativistic absolute temperature should
be introduced operationally via relativistic Carnot processes. We exhibit the
more implicit or even hidden tacit preassumptions being made and point to a
couple of gaps, errors and inconclusive statements in some of the existing
literature. We show in particular that there is a wide-spread habit to draw
general conclusions from the analysis of too restricted and special
thermodynamic processes, e.g. processes with constant pressure, which is
dangerous and sometimes leads to wrong results. Furthermore, we give a detailed
analysis of the so-called zeroth law of relativistic thermodynamics with the
help of a relativistic Carnot process. We rigorously show that, contrary to
certain statements in the literature, thermodynamic systems at different
relativistic temperatures, moving relative to each other, can thermally stably
coexist provided that their respective temperatures obey a certain functional
relation (given by the Lorentz factor). This implies however that their
respective rest temperatures are the same.
|
[
{
"created": "Thu, 17 Jan 2008 09:43:50 GMT",
"version": "v1"
}
] |
2008-01-21
|
[
[
"Requardt",
"Manfred",
""
]
] |
In this paper we carefully reexamine the various framworks existing in the field of relativistic thermodynamics. We scrutinize in particular the different conceptual foundations of notions like the relativistic work, heat force, moving heat and relativistic temperature. As to the latter notion we argue that, as in ordinary thermodynamics, relativistic absolute temperature should be introduced operationally via relativistic Carnot processes. We exhibit the more implicit or even hidden tacit preassumptions being made and point to a couple of gaps, errors and inconclusive statements in some of the existing literature. We show in particular that there is a wide-spread habit to draw general conclusions from the analysis of too restricted and special thermodynamic processes, e.g. processes with constant pressure, which is dangerous and sometimes leads to wrong results. Furthermore, we give a detailed analysis of the so-called zeroth law of relativistic thermodynamics with the help of a relativistic Carnot process. We rigorously show that, contrary to certain statements in the literature, thermodynamic systems at different relativistic temperatures, moving relative to each other, can thermally stably coexist provided that their respective temperatures obey a certain functional relation (given by the Lorentz factor). This implies however that their respective rest temperatures are the same.
|
0801.2850
|
Claudio Dappiaggi
|
Claudio Dappiaggi, Klaus Fredenhagen and Nicola Pinamonti
|
Stable cosmological models driven by a free quantum scalar field
|
8 pages, 1 figure and revtex. Comments and references added
|
Phys.Rev.D77:104015,2008
|
10.1103/PhysRevD.77.104015
|
Desy 08-006, ZMP-HH/08-1
|
gr-qc hep-th
| null |
In the mathematically rigorous analysis of semiclassical Einstein's
equations, the renormalisation of the stress-energy tensor plays a crucial
role. We address such a topic in the case of a scalar field with both arbitrary
mass and coupling with gravity in the hypothesis that the underlying algebraic
quantum state is of Hadamard type. Particularly, if we focus on highly
symmetric solutions of the semiclassical Einstein's equations, the envisaged
method displays a de Sitter type behaviour even without an a priori introduced
cosmological constant. As a further novel result we shall show that these
solutions turn out to be stable.
|
[
{
"created": "Fri, 18 Jan 2008 15:24:51 GMT",
"version": "v1"
},
{
"created": "Fri, 1 Feb 2008 16:12:36 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Dappiaggi",
"Claudio",
""
],
[
"Fredenhagen",
"Klaus",
""
],
[
"Pinamonti",
"Nicola",
""
]
] |
In the mathematically rigorous analysis of semiclassical Einstein's equations, the renormalisation of the stress-energy tensor plays a crucial role. We address such a topic in the case of a scalar field with both arbitrary mass and coupling with gravity in the hypothesis that the underlying algebraic quantum state is of Hadamard type. Particularly, if we focus on highly symmetric solutions of the semiclassical Einstein's equations, the envisaged method displays a de Sitter type behaviour even without an a priori introduced cosmological constant. As a further novel result we shall show that these solutions turn out to be stable.
|
1812.10879
|
Nikolaos Dimakis
|
A. Karagiorgos, T. Pailas, N. Dimakis, G. O. Papadopoulos, Petros A.
Terzis and T. Christodoulakis
|
Quantum cosmology of Bianchi VIII, IX LRS geometries
|
LaTeX2e source file, 16 pages, 2 figures
| null |
10.1088/1475-7516/2019/04/006
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the present work we revisit the axisymmetric Bianchi VIII and IX models.
At the classical level we reproduce the known analytic solution, in a novel way
making use of two quadratic integrals of motion, the constraint equation, as
well as a linear non-local integral of motion. These quantities correspond to
two second rank Killing tensors and a homothetic vector field existing on the
relevant configuration space. On the corresponding phase space the two
quadratic charges commute with the Hamiltonian constraint but not among
themselves. Thus, after turning these charges into operators we obtain two
different solutions to the Wheeler DeWitt equation utilizing each of the
quadratic operators. The homothetic vector is then used, as a natural guide
line, to define a normalizable conditional probability which assigns zero to
the classically collapsed configurations.
|
[
{
"created": "Fri, 28 Dec 2018 03:14:21 GMT",
"version": "v1"
}
] |
2019-04-10
|
[
[
"Karagiorgos",
"A.",
""
],
[
"Pailas",
"T.",
""
],
[
"Dimakis",
"N.",
""
],
[
"Papadopoulos",
"G. O.",
""
],
[
"Terzis",
"Petros A.",
""
],
[
"Christodoulakis",
"T.",
""
]
] |
In the present work we revisit the axisymmetric Bianchi VIII and IX models. At the classical level we reproduce the known analytic solution, in a novel way making use of two quadratic integrals of motion, the constraint equation, as well as a linear non-local integral of motion. These quantities correspond to two second rank Killing tensors and a homothetic vector field existing on the relevant configuration space. On the corresponding phase space the two quadratic charges commute with the Hamiltonian constraint but not among themselves. Thus, after turning these charges into operators we obtain two different solutions to the Wheeler DeWitt equation utilizing each of the quadratic operators. The homothetic vector is then used, as a natural guide line, to define a normalizable conditional probability which assigns zero to the classically collapsed configurations.
|
2011.13616
|
Jaroslav Vrba
|
Jaroslav Vrba, Martin Urbanec, Zden\v{e}k Stuchl\'ik and John C.
Miller
|
Trapping of null geodesics in slowly rotating spacetimes
| null | null |
10.1140/epjc/s10052-020-08642-z
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Extremely compact objects containing a region of trapped null geodesics could
be of astrophysical relevance due to trapping of neutrinos with consequent
impact on cooling processes or trapping of gravitational waves. These objects
have previously been studied under the assumption of spherical symmetry. In the
present paper, we consider a simple generalization by studying trapping of null
geodesics in the framework of the Hartle-Thorne slow-rotation approximation
taken to first order in the angular velocity, and considering a uniform-density
object with uniform emissivity for the null geodesics. We calculate effective
potentials and escape cones for the null geodesics and how they depend on the
parameters of the spacetimes, and also calculate the "local" and "global"
coefficients of efficiency for the trapping. We demonstrate that due to the
rotation the trapping efficiency is different for co-rotating and retrograde
null geodesics, and that trapping can occur even for $R>3GM/c^2$, contrary to
what happens in the absence of rotation.
|
[
{
"created": "Fri, 27 Nov 2020 09:14:00 GMT",
"version": "v1"
}
] |
2020-11-30
|
[
[
"Vrba",
"Jaroslav",
""
],
[
"Urbanec",
"Martin",
""
],
[
"Stuchlík",
"Zdeněk",
""
],
[
"Miller",
"John C.",
""
]
] |
Extremely compact objects containing a region of trapped null geodesics could be of astrophysical relevance due to trapping of neutrinos with consequent impact on cooling processes or trapping of gravitational waves. These objects have previously been studied under the assumption of spherical symmetry. In the present paper, we consider a simple generalization by studying trapping of null geodesics in the framework of the Hartle-Thorne slow-rotation approximation taken to first order in the angular velocity, and considering a uniform-density object with uniform emissivity for the null geodesics. We calculate effective potentials and escape cones for the null geodesics and how they depend on the parameters of the spacetimes, and also calculate the "local" and "global" coefficients of efficiency for the trapping. We demonstrate that due to the rotation the trapping efficiency is different for co-rotating and retrograde null geodesics, and that trapping can occur even for $R>3GM/c^2$, contrary to what happens in the absence of rotation.
|
gr-qc/9306001
| null |
Yu.A. Kubyshin and J.I. Perez Cadenas
|
Compactification to Non-symmetric Homogeneous Space in Multidimensional
Einstein-Yang-Mills Theory
|
23 pages, LATEX, UB-ECM-PF 93/11
| null | null | null |
gr-qc
| null |
We study ten-dimensional Einstein-Yang-Mills model with the space of extra
dimensions being a non-symmetric homogeneous space with the invariant metric
parametrized by two scales. Dimensional reduction of the model is carried out
and the scalar potential of the reduced theory is calculated. In a cosmological
setting minima of the potential in the radiation-dominated period that followed
the inflation are found and their stability is analyzed. The compactifying
solution is shown to be stable for the appropriate values of parameters.
|
[
{
"created": "Tue, 1 Jun 1993 13:32:23 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Kubyshin",
"Yu. A.",
""
],
[
"Cadenas",
"J. I. Perez",
""
]
] |
We study ten-dimensional Einstein-Yang-Mills model with the space of extra dimensions being a non-symmetric homogeneous space with the invariant metric parametrized by two scales. Dimensional reduction of the model is carried out and the scalar potential of the reduced theory is calculated. In a cosmological setting minima of the potential in the radiation-dominated period that followed the inflation are found and their stability is analyzed. The compactifying solution is shown to be stable for the appropriate values of parameters.
|
gr-qc/0608120
|
Peter K.F. Kuhfittig
|
Peter K. F. Kuhfittig
|
On a time-dependent extra spatial dimension
|
Invited talk at the Fifth International Conference of Applied
Mathematics and Computing in Plovdiv, Bulgaria (August, 2008)
|
Int. J. of Pure and Appl. Math., vol. 49, no. 4, pp. 577-582, 2008
| null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the usual brane-world scenario matter fields are confined to the
four-dimensional spacetime, called a 3-brane, embedded in a higher-dimensional
space, usually referred to as the bulk spacetime. In this paper we assume that
the 3-brane is a de Sitter space; there is only one extra spatial dimension,
assumed to be time dependent. By using the form of the brane-world
energy-momentum tensor suggested by Shiromizu et al. in the five-dimensional
Einstein equations, it is proposed that the cosmological expansion of the
3-brane may provide a possible explanation for the collapse of the extra
dimension, as well as for the energy stored in the resulting curled-up
dimension. More precisely, whenever the bulk cosmological constant \Lambda is
negative, the extra spatial dimension rapidly shrinks during the inflation of
the brane. When \Lambda is positive, on the other hand, the extra spatial
dimension either completely follows the cosmological expansion of the brane or
completely ignores it, thereby shrinking relative to the expanding space. This
behavior resembles the all-or-nothing behavior of ordinary systems in an
expanding universe, as recently demonstrated by R.H. Price.
|
[
{
"created": "Mon, 28 Aug 2006 17:01:51 GMT",
"version": "v1"
},
{
"created": "Tue, 22 May 2007 18:59:12 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Jan 2009 14:36:55 GMT",
"version": "v3"
},
{
"created": "Mon, 23 Feb 2009 19:46:36 GMT",
"version": "v4"
},
{
"created": "Mon, 14 May 2012 14:28:57 GMT",
"version": "v5"
}
] |
2012-05-15
|
[
[
"Kuhfittig",
"Peter K. F.",
""
]
] |
In the usual brane-world scenario matter fields are confined to the four-dimensional spacetime, called a 3-brane, embedded in a higher-dimensional space, usually referred to as the bulk spacetime. In this paper we assume that the 3-brane is a de Sitter space; there is only one extra spatial dimension, assumed to be time dependent. By using the form of the brane-world energy-momentum tensor suggested by Shiromizu et al. in the five-dimensional Einstein equations, it is proposed that the cosmological expansion of the 3-brane may provide a possible explanation for the collapse of the extra dimension, as well as for the energy stored in the resulting curled-up dimension. More precisely, whenever the bulk cosmological constant \Lambda is negative, the extra spatial dimension rapidly shrinks during the inflation of the brane. When \Lambda is positive, on the other hand, the extra spatial dimension either completely follows the cosmological expansion of the brane or completely ignores it, thereby shrinking relative to the expanding space. This behavior resembles the all-or-nothing behavior of ordinary systems in an expanding universe, as recently demonstrated by R.H. Price.
|
1909.01988
|
Ashis Saha
|
Anish Das, Ashis Saha, Sunandan Gangopadhyay
|
Shadow of charged black holes in Gauss-Bonnet gravity
|
18 pages Latex, comments are welcome
|
Eur. Phys. J. C 80, 180 (2020)
|
10.1140/epjc/s10052-020-7726-z
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper, we investigate the effect of higher curvature corrections from
Gauss-Bonnet gravity on the shadow of charged black holes in both $AdS$ and
Minkowski spacetimes. The null geodesic equations are computed in $d=5$
spacetime dimensions by using the directions of symmetries and Hamilton-Jacobi
equation. With the null geodesics in hand, we then proceed to evaluate the
celestial coordinates ($\alpha, \beta$) and the radius $R_s$ of the black hole
shadow and represent it graphically. The effects of charge $Q$ of the black
hole and the Gauss-Bonnet parameter $\gamma$ on the radius of the shadow $R_s$
is studied in detail. It is observed that the Gauss-Bonnet parameter $\gamma$
affects the radius of the black hole shadow $R_s$ differently for the $AdS$
black hole spacetime in comparison to the black hole spacetime which is
asymptotically flat. In particular the radius of the black hole shadow
increases with increase in the Gauss-Bonnet parameter in case of the $AdS$
black hole spacetime and decreases in case of the asymptotically flat black
hole spacetime. We then introduce a plasma background in order to observe the
change in the silhouette of the black hole shadow due to a change in the
refractive index of the plasma medium. Finally, we study the effect of the
Gauss-Bonnet parameter $\gamma$ on the energy emission rate of the black hole
which depends on the black hole shadow radius and represent the results
graphically.
|
[
{
"created": "Wed, 4 Sep 2019 12:27:00 GMT",
"version": "v1"
}
] |
2020-02-28
|
[
[
"Das",
"Anish",
""
],
[
"Saha",
"Ashis",
""
],
[
"Gangopadhyay",
"Sunandan",
""
]
] |
In this paper, we investigate the effect of higher curvature corrections from Gauss-Bonnet gravity on the shadow of charged black holes in both $AdS$ and Minkowski spacetimes. The null geodesic equations are computed in $d=5$ spacetime dimensions by using the directions of symmetries and Hamilton-Jacobi equation. With the null geodesics in hand, we then proceed to evaluate the celestial coordinates ($\alpha, \beta$) and the radius $R_s$ of the black hole shadow and represent it graphically. The effects of charge $Q$ of the black hole and the Gauss-Bonnet parameter $\gamma$ on the radius of the shadow $R_s$ is studied in detail. It is observed that the Gauss-Bonnet parameter $\gamma$ affects the radius of the black hole shadow $R_s$ differently for the $AdS$ black hole spacetime in comparison to the black hole spacetime which is asymptotically flat. In particular the radius of the black hole shadow increases with increase in the Gauss-Bonnet parameter in case of the $AdS$ black hole spacetime and decreases in case of the asymptotically flat black hole spacetime. We then introduce a plasma background in order to observe the change in the silhouette of the black hole shadow due to a change in the refractive index of the plasma medium. Finally, we study the effect of the Gauss-Bonnet parameter $\gamma$ on the energy emission rate of the black hole which depends on the black hole shadow radius and represent the results graphically.
|
gr-qc/0003105
|
Matt Visser
|
Stefano Liberati (SISSA, Trieste), Sebastiano Sonego (U Udine), Matt
Visser (Washington University in Saint Louis)
|
Unexpectedly large surface gravities for acoustic horizons?
|
Plain LaTeX2e, 32 pages, 10 encapsulated postscript figures; Revised
in view of referee comments; More discussion, (role of viscosity,
relationship with other models), more references; physics and presentation
clarified but central conclusions unaltered
|
Class.Quant.Grav.17:2903,2000
|
10.1088/0264-9381/17/15/305
| null |
gr-qc
| null |
Acoustic black holes are fluid dynamic analogs of general relativistic black
holes, wherein the behaviour of sound waves in a moving fluid acts as an analog
for scalar fields propagating in a gravitational background. Acoustic horizons
possess many of the properties more normally associated with the event horizons
of general relativity, up to and including Hawking radiation. They have
received much attention because it would seem to be much easier to
experimentally create an acoustic horizon than to create an event horizon. We
wish to point out some potential difficulties (and opportunities) in actually
setting up an experiment that possesses an acoustic horizon. We show that in
zero-viscosity, stationary fluid flow with generic boundary conditions, the
creation of an acoustic horizon is accompanied by a formally infinite ``surface
gravity'', and a formally infinite Hawking flux. Only by applying a suitable
non-constant external body force, and for very specific boundary conditions on
the flow, can these quantities be kept finite. This problem is ameliorated in
more realistic models of the fluid. For instance, adding viscosity always makes
the Hawking flux finite, but greatly complicates the behaviour of the acoustic
radiation --- viscosity is tantamount to explicitly breaking ``acoustic Lorentz
invariance''. Thus, this issue represents both a difficulty and an opportunity
--- acoustic horizons may be somewhat more difficult to form than naively
envisaged, but if formed, they may be much easier to detect than one would at
first suppose.
|
[
{
"created": "Tue, 28 Mar 2000 22:21:18 GMT",
"version": "v1"
},
{
"created": "Tue, 30 May 2000 21:02:45 GMT",
"version": "v2"
}
] |
2008-11-26
|
[
[
"Liberati",
"Stefano",
"",
"SISSA, Trieste"
],
[
"Sonego",
"Sebastiano",
"",
"U Udine"
],
[
"Visser",
"Matt",
"",
"Washington University in Saint Louis"
]
] |
Acoustic black holes are fluid dynamic analogs of general relativistic black holes, wherein the behaviour of sound waves in a moving fluid acts as an analog for scalar fields propagating in a gravitational background. Acoustic horizons possess many of the properties more normally associated with the event horizons of general relativity, up to and including Hawking radiation. They have received much attention because it would seem to be much easier to experimentally create an acoustic horizon than to create an event horizon. We wish to point out some potential difficulties (and opportunities) in actually setting up an experiment that possesses an acoustic horizon. We show that in zero-viscosity, stationary fluid flow with generic boundary conditions, the creation of an acoustic horizon is accompanied by a formally infinite ``surface gravity'', and a formally infinite Hawking flux. Only by applying a suitable non-constant external body force, and for very specific boundary conditions on the flow, can these quantities be kept finite. This problem is ameliorated in more realistic models of the fluid. For instance, adding viscosity always makes the Hawking flux finite, but greatly complicates the behaviour of the acoustic radiation --- viscosity is tantamount to explicitly breaking ``acoustic Lorentz invariance''. Thus, this issue represents both a difficulty and an opportunity --- acoustic horizons may be somewhat more difficult to form than naively envisaged, but if formed, they may be much easier to detect than one would at first suppose.
|
2302.10875
|
Hongsheng Zhang
|
Kai Lin, Chieh-Hung Chen, Yang-Yi Sun, Xilong Fan, Hongsheng Zhang
|
Echoes of Stars in tracking Rastall gravity
|
11 pages, 3 figs
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We construct a star with uniform density in frame of tracking Rastall
gravity, in which the density of effective dark matter tracks the density of
dark energy. To demonstrate stability of the star we analyse the axial
gravitational perturbations of the star. We find that echo wavelets naturally
appear in the axial gravitational waves when the dark matter plays a
significant role in construction of the star. We show that the physical origin
of this echo roots in the potential valley near the surface of star. This
effect leads to a clue to detect Rastall dark energy from the ringdown phase of
gravitational wave from binary stars enriched by dark matter.
|
[
{
"created": "Fri, 17 Feb 2023 10:07:26 GMT",
"version": "v1"
}
] |
2023-02-22
|
[
[
"Lin",
"Kai",
""
],
[
"Chen",
"Chieh-Hung",
""
],
[
"Sun",
"Yang-Yi",
""
],
[
"Fan",
"Xilong",
""
],
[
"Zhang",
"Hongsheng",
""
]
] |
We construct a star with uniform density in frame of tracking Rastall gravity, in which the density of effective dark matter tracks the density of dark energy. To demonstrate stability of the star we analyse the axial gravitational perturbations of the star. We find that echo wavelets naturally appear in the axial gravitational waves when the dark matter plays a significant role in construction of the star. We show that the physical origin of this echo roots in the potential valley near the surface of star. This effect leads to a clue to detect Rastall dark energy from the ringdown phase of gravitational wave from binary stars enriched by dark matter.
|
gr-qc/9912080
|
Mohammad Vahid Takook
|
J-P. Gazeau, M.V. Takook
|
"Massive" vector field in de Sitter space
|
15 pages
|
J.Math.Phys. 41 (2000) 5920-5933; J.Math.Phys. 43 (2002) 6379
|
10.1063/1.1287641
| null |
gr-qc
| null |
We present in this paper a covariant quantization of the ``massive'' vector
field on de Sitter (dS) space based on analyticity in the complexified
pseudo-Riemanian manifold. The correspondence between unitary irreducible
representations of the de Sitter group and the field theory on de Sitter
space-time is essential in our approach. We introduce the Wightman-G\"arding
axiomatic for vector field on dS space. The Hilbert space structure and the
unsmeared field operators $K_\alpha(x)$ are also defined. This work is in the
direct continuation of previous one concerning the scalar and the spinor cases.
|
[
{
"created": "Sun, 19 Dec 1999 07:24:37 GMT",
"version": "v1"
}
] |
2009-10-31
|
[
[
"Gazeau",
"J-P.",
""
],
[
"Takook",
"M. V.",
""
]
] |
We present in this paper a covariant quantization of the ``massive'' vector field on de Sitter (dS) space based on analyticity in the complexified pseudo-Riemanian manifold. The correspondence between unitary irreducible representations of the de Sitter group and the field theory on de Sitter space-time is essential in our approach. We introduce the Wightman-G\"arding axiomatic for vector field on dS space. The Hilbert space structure and the unsmeared field operators $K_\alpha(x)$ are also defined. This work is in the direct continuation of previous one concerning the scalar and the spinor cases.
|
gr-qc/9905010
|
Garcia
|
L.C.Garcia de Andrade
|
Global monopoles and massless dilatons in Einstein-Cartan gravity
|
Latex file,10 K
| null | null | null |
gr-qc
| null |
A global monopole in dilatonic Einstein-Cartan gravity is presented. A
linearized solution representing a global monopole interacting with a massless
dilaton is found where Cartan torsion does not interact with the monopole Higgs
field.Computation of the geodesic equation shows that the monopole-dilaton
system generates a repulsive gravitational field.The solution is shown to break
the linear approximation for certain values of torsion.
|
[
{
"created": "Tue, 4 May 1999 09:29:09 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"de Andrade",
"L. C. Garcia",
""
]
] |
A global monopole in dilatonic Einstein-Cartan gravity is presented. A linearized solution representing a global monopole interacting with a massless dilaton is found where Cartan torsion does not interact with the monopole Higgs field.Computation of the geodesic equation shows that the monopole-dilaton system generates a repulsive gravitational field.The solution is shown to break the linear approximation for certain values of torsion.
|
gr-qc/9211004
| null |
Jonathan Halliwell and Miguel Ortiz
|
Sum-over-histories origin of the composition laws of relativistic
quantum mechanics and quantum cosmology
|
36 pages
|
Phys.Rev. D48 (1993) 748-768
|
10.1103/PhysRevD.48.748
|
CTP# 2134
|
gr-qc hep-th
| null |
The scope of the paper has been broadened to include a more complete
discussion of the following topics: The derivation of composition laws in
quantum cosmology. The connection between the existence of a composition law in
the sum over histories approach to relativistic quantum mechanics and quantum
cosmology, and the existence of a canonical formulation.
|
[
{
"created": "Wed, 4 Nov 1992 21:33:16 GMT",
"version": "v1"
},
{
"created": "Wed, 27 Jan 1993 20:45:11 GMT",
"version": "v2"
}
] |
2009-10-22
|
[
[
"Halliwell",
"Jonathan",
""
],
[
"Ortiz",
"Miguel",
""
]
] |
The scope of the paper has been broadened to include a more complete discussion of the following topics: The derivation of composition laws in quantum cosmology. The connection between the existence of a composition law in the sum over histories approach to relativistic quantum mechanics and quantum cosmology, and the existence of a canonical formulation.
|
gr-qc/9210008
|
Jeff Greensite
|
J. Greensite
|
Dynamical Origin of the Lorentzian Signature of Spacetime
|
6 pages, LaTeX
|
Phys.Lett. B300 (1993) 34-37
|
10.1016/0370-2693(93)90744-3
|
NBI-HE-92-59
|
gr-qc hep-th
| null |
It is suggested that not only the curvature, but also the signature of
spacetime is subject to quantum fluctuations. A generalized D-dimensional
spacetime metric of the form $g_{\mu \nu}=e^a_\mu \eta_{ab} e^b_\nu$ is
introduced, where $\eta_{ab} = diag\{e^{i\theta},1,...,1\}$. The corresponding
functional integral for quantized fields then interpolates from a Euclidean
path integral in Euclidean space, at $\theta=0$, to a Feynman path integral in
Minkowski space, at $\theta=\pi$. Treating the phase $e^{i\theta}$ as just
another quantized field, the signature of spacetime is determined dynamically
by its expectation value. The complex-valued effective potential $V(\theta)$
for the phase field, induced by massless fields at one-loop, is considered. It
is argued that $Re[V(\theta)]$ is minimized and $Im[V(\theta)]$ is stationary,
uniquely in D=4 dimensions, at $\theta=\pi$, which suggests a dynamical origin
for the Lorentzian signature of spacetime.
|
[
{
"created": "Wed, 14 Oct 1992 21:02:16 GMT",
"version": "v1"
}
] |
2009-10-22
|
[
[
"Greensite",
"J.",
""
]
] |
It is suggested that not only the curvature, but also the signature of spacetime is subject to quantum fluctuations. A generalized D-dimensional spacetime metric of the form $g_{\mu \nu}=e^a_\mu \eta_{ab} e^b_\nu$ is introduced, where $\eta_{ab} = diag\{e^{i\theta},1,...,1\}$. The corresponding functional integral for quantized fields then interpolates from a Euclidean path integral in Euclidean space, at $\theta=0$, to a Feynman path integral in Minkowski space, at $\theta=\pi$. Treating the phase $e^{i\theta}$ as just another quantized field, the signature of spacetime is determined dynamically by its expectation value. The complex-valued effective potential $V(\theta)$ for the phase field, induced by massless fields at one-loop, is considered. It is argued that $Re[V(\theta)]$ is minimized and $Im[V(\theta)]$ is stationary, uniquely in D=4 dimensions, at $\theta=\pi$, which suggests a dynamical origin for the Lorentzian signature of spacetime.
|
2009.06339
|
Thomas Buchert
|
Ismael Delgado Gaspar and Thomas Buchert
|
Lagrangian theory of structure formation in relativistic cosmology. VI.
Comparison with Szekeres exact solutions
|
27 pages, 1 figure; matches published version in PRD
|
Phys. Rev. D 103, 023513 (2021)
|
10.1103/PhysRevD.103.023513
| null |
gr-qc astro-ph.CO
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We examine the relation between the Szekeres models and relativistic
Lagrangian perturbation schemes, in particular the Relativistic Zel'dovich
Approximation (RZA). We show that the second class of the Szekeres solutions is
exactly contained within the RZA when the latter is restricted to an
irrotational dust source with a flow-orthogonal foliation of spacetime. In such
a case, the solution is governed by the first principal scalar invariant of the
deformation field, proving a direct connection with a class of Newtonian
three-dimensional solutions without symmetry. For the second class, a necessary
and sufficient condition for the vanishing of cosmological backreaction on a
scale of homogeneity is expressed through integral constraints. Domains with no
backreaction can be smoothly matched, forming a lattice model, where exact
deviations average out at a given scale of homogeneity, and the homogeneous and
isotropic background is recovered as an average property of the model. Although
the connection with the first class of Szekeres solutions is not
straightforward, this class allows for the interpretation in terms of a spatial
superposition of nonintersecting fluid lines, where each world line evolves
independently and under the RZA model equations, but with different associated
`local backgrounds'. This points to the possibility of generalizing the
Lagrangian perturbation schemes to structure formation models on evolving
backgrounds, including global cosmological backreaction.
|
[
{
"created": "Mon, 14 Sep 2020 11:57:07 GMT",
"version": "v1"
},
{
"created": "Wed, 6 Jan 2021 17:58:17 GMT",
"version": "v2"
}
] |
2021-01-07
|
[
[
"Gaspar",
"Ismael Delgado",
""
],
[
"Buchert",
"Thomas",
""
]
] |
We examine the relation between the Szekeres models and relativistic Lagrangian perturbation schemes, in particular the Relativistic Zel'dovich Approximation (RZA). We show that the second class of the Szekeres solutions is exactly contained within the RZA when the latter is restricted to an irrotational dust source with a flow-orthogonal foliation of spacetime. In such a case, the solution is governed by the first principal scalar invariant of the deformation field, proving a direct connection with a class of Newtonian three-dimensional solutions without symmetry. For the second class, a necessary and sufficient condition for the vanishing of cosmological backreaction on a scale of homogeneity is expressed through integral constraints. Domains with no backreaction can be smoothly matched, forming a lattice model, where exact deviations average out at a given scale of homogeneity, and the homogeneous and isotropic background is recovered as an average property of the model. Although the connection with the first class of Szekeres solutions is not straightforward, this class allows for the interpretation in terms of a spatial superposition of nonintersecting fluid lines, where each world line evolves independently and under the RZA model equations, but with different associated `local backgrounds'. This points to the possibility of generalizing the Lagrangian perturbation schemes to structure formation models on evolving backgrounds, including global cosmological backreaction.
|
gr-qc/0701034
|
Mihalis Dafermos
|
Mihalis Dafermos and Alan D. Rendall
|
Strong cosmic censorship for surface-symmetric cosmological spacetimes
with collisionless matter
|
83 pages, 16 figures
| null | null | null |
gr-qc math.AP math.DG
| null |
This paper addresses strong cosmic censorship for spacetimes with
self-gravitating collisionless matter, evolving from surface-symmetric compact
initial data. The global dynamics exhibit qualitatively different features
according to the sign of the curvature $k$ of the symmetric surfaces and the
cosmological constant $\Lambda$. With a suitable formulation, the question of
strong cosmic censorship is settled in the affirmative if $\Lambda=0$ or
$k\le0$, $\Lambda>0$. In the case $\Lambda>0$, $k=1$, we give a detailed
geometric characterization of possible "boundary" components of spacetime; the
remaining obstruction to showing strong cosmic censorship in this case has to
do with the possible formation of extremal Schwarzschild-de Sitter-type black
holes. In the special case that the initial symmetric surfaces are all
expanding, strong cosmic censorship is shown in the past for all $k,\Lambda$.
Finally, our results also lead to a geometric characterization of the future
boundary of black hole interiors for the collapse of asymptotically flat data:
in particular, in the case of small perturbations of Schwarzschild data, it is
shown that these solutions do not exhibit Cauchy horizons emanating from $i^+$
with strictly positive limiting area radius.
|
[
{
"created": "Fri, 5 Jan 2007 12:37:21 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Dafermos",
"Mihalis",
""
],
[
"Rendall",
"Alan D.",
""
]
] |
This paper addresses strong cosmic censorship for spacetimes with self-gravitating collisionless matter, evolving from surface-symmetric compact initial data. The global dynamics exhibit qualitatively different features according to the sign of the curvature $k$ of the symmetric surfaces and the cosmological constant $\Lambda$. With a suitable formulation, the question of strong cosmic censorship is settled in the affirmative if $\Lambda=0$ or $k\le0$, $\Lambda>0$. In the case $\Lambda>0$, $k=1$, we give a detailed geometric characterization of possible "boundary" components of spacetime; the remaining obstruction to showing strong cosmic censorship in this case has to do with the possible formation of extremal Schwarzschild-de Sitter-type black holes. In the special case that the initial symmetric surfaces are all expanding, strong cosmic censorship is shown in the past for all $k,\Lambda$. Finally, our results also lead to a geometric characterization of the future boundary of black hole interiors for the collapse of asymptotically flat data: in particular, in the case of small perturbations of Schwarzschild data, it is shown that these solutions do not exhibit Cauchy horizons emanating from $i^+$ with strictly positive limiting area radius.
|
1304.1595
|
Chi Xiong
|
Kerson Huang, Chi Xiong, Xiaofei Zhao
|
Scalar-field theory of dark matter
|
25 pages, 9 figures. A new section "Long-ranged force induced by the
scalar field" is added, plus a few clarifications in the paper. References
updated. To appear in International Journal of Modern Physics A
|
International Journal of Modern Physics A, Vol. 29 (2014) 1450074
|
10.1142/S0217751X14500742
|
NTU-IAS-009
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We develop a theory of dark matter based on a previously proposed picture, in
which a complex vacuum scalar field makes the universe a superfluid, with the
energy density of the superfluid giving rise to dark energy, and variations
from vacuum density giving rise to dark matter. We formulate a nonlinear
Klein-Gordon equation to describe the superfluid, treating galaxies as external
sources. We study the response of the superfluid to the galaxies, in
particular, the emergence of the dark-matter galactic halo, contortions during
galaxy collisions, and the creation of vortices due to galactic rotation.
|
[
{
"created": "Fri, 5 Apr 2013 01:37:05 GMT",
"version": "v1"
},
{
"created": "Tue, 29 Apr 2014 09:24:10 GMT",
"version": "v2"
}
] |
2014-04-30
|
[
[
"Huang",
"Kerson",
""
],
[
"Xiong",
"Chi",
""
],
[
"Zhao",
"Xiaofei",
""
]
] |
We develop a theory of dark matter based on a previously proposed picture, in which a complex vacuum scalar field makes the universe a superfluid, with the energy density of the superfluid giving rise to dark energy, and variations from vacuum density giving rise to dark matter. We formulate a nonlinear Klein-Gordon equation to describe the superfluid, treating galaxies as external sources. We study the response of the superfluid to the galaxies, in particular, the emergence of the dark-matter galactic halo, contortions during galaxy collisions, and the creation of vortices due to galactic rotation.
|
1409.6513
|
Pardyumn Kumar Sahoo
|
P.K. Sahoo, K.L. Mahanta, D. Goit, A.K. Sihna, S. S. Xulu, U.R. Das,
A. Prasad and R. Prasad
|
Einstein energy-momentum complex for a phantom black hole metric
|
5 pages, 2 figures
|
Chin. Phys. Lett. Vol. 32, No. 02 (2015) 020402
|
10.1088/0256-307X/32/2/020402
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we calculate the energy distribution E(r) associated with a
static spherically symmetric non-singular phantom black hole metric in
Einstein's prescription in general relativity. As required for Einstein
energy-momentum complex, we perform calculations in quasi-Cartesian
coordinates. We also calculate momentum components and get zero values as
expected from the geometry of the metric.
|
[
{
"created": "Sun, 14 Sep 2014 11:04:58 GMT",
"version": "v1"
},
{
"created": "Fri, 16 Jan 2015 04:09:40 GMT",
"version": "v2"
}
] |
2017-04-19
|
[
[
"Sahoo",
"P. K.",
""
],
[
"Mahanta",
"K. L.",
""
],
[
"Goit",
"D.",
""
],
[
"Sihna",
"A. K.",
""
],
[
"Xulu",
"S. S.",
""
],
[
"Das",
"U. R.",
""
],
[
"Prasad",
"A.",
""
],
[
"Prasad",
"R.",
""
]
] |
In this paper we calculate the energy distribution E(r) associated with a static spherically symmetric non-singular phantom black hole metric in Einstein's prescription in general relativity. As required for Einstein energy-momentum complex, we perform calculations in quasi-Cartesian coordinates. We also calculate momentum components and get zero values as expected from the geometry of the metric.
|
gr-qc/0502004
|
Marco Spaans
|
M. Spaans
|
A Background Independent Description of Physical Processes
|
Text rewritten for clarity, with emphasis on physical ideas
| null | null | null |
gr-qc hep-ph hep-th math-ph math.MP
| null |
A mathematical structure is presented that allows one to define a physical
process independent of any background. That is, it is possible, for a set of
objects, to choose an object from that set through a choice process that is
defined solely in terms of the objects in the set itself. It is conjectured
that this background free structure is a necessary ingredient for a
self-consistent description of physical processes and that these same physical
processes are determined by the absence of any background. The properties of
the mathematical structure, denoted Q, are equivalent to the three-dimensional
topological manifold 2T^3 + 3(S^1 x S^2), two three-tori plus three handles,
embedded in four dimensions. The topology of Q reproduces the basic properties
of QED and Einstein gravity.
|
[
{
"created": "Tue, 1 Feb 2005 19:27:03 GMT",
"version": "v1"
},
{
"created": "Sat, 26 Mar 2005 09:36:38 GMT",
"version": "v2"
},
{
"created": "Sun, 14 Jan 2007 15:21:25 GMT",
"version": "v3"
}
] |
2007-05-23
|
[
[
"Spaans",
"M.",
""
]
] |
A mathematical structure is presented that allows one to define a physical process independent of any background. That is, it is possible, for a set of objects, to choose an object from that set through a choice process that is defined solely in terms of the objects in the set itself. It is conjectured that this background free structure is a necessary ingredient for a self-consistent description of physical processes and that these same physical processes are determined by the absence of any background. The properties of the mathematical structure, denoted Q, are equivalent to the three-dimensional topological manifold 2T^3 + 3(S^1 x S^2), two three-tori plus three handles, embedded in four dimensions. The topology of Q reproduces the basic properties of QED and Einstein gravity.
|
gr-qc/0504046
|
Damir Buskulic
|
F. Beauville, D. Buskulic, R. Flaminio, R. Gouaty, D. Grosjean, F.
Marion, B. Mours, E. Tournefier, D. Verkindt, M. Yvert
|
Variable placement of templates technique in a 2D parameter space for
binary inspiral searches
|
28 pages, 28 figures,submitted to CQG, fixed typos, added sections
following referees comments
|
Class.Quant.Grav. 22 (2005) 4285-4309
|
10.1088/0264-9381/22/20/010
| null |
gr-qc
| null |
In the search for binary systems inspiral signal in interferometric
gravitational waves detectors, one needs the generation and placement of a grid
of templates. We present an original technique for the placement in the
associated parameter space, that makes use of the variation of size of the
isomatch ellipses in order to reduce the number of templates necessary to cover
the parameter space. This technique avoids the potentially expensive
computation of the metric at every point, at the cost of having a small number
of ``holes'' in the coverage, representing a few percent of the surface of the
parameter space, where the match is slightly lower than specified. A study of
the covering efficiency, as well as a comparison with a very simple regular
tiling using a single ellipse is made. Simulations show an improvement varying
between 6% and 30% for the computing cost in this comparison.
|
[
{
"created": "Tue, 12 Apr 2005 08:26:21 GMT",
"version": "v1"
},
{
"created": "Wed, 31 Aug 2005 10:08:35 GMT",
"version": "v2"
}
] |
2009-11-11
|
[
[
"Beauville",
"F.",
""
],
[
"Buskulic",
"D.",
""
],
[
"Flaminio",
"R.",
""
],
[
"Gouaty",
"R.",
""
],
[
"Grosjean",
"D.",
""
],
[
"Marion",
"F.",
""
],
[
"Mours",
"B.",
""
],
[
"Tournefier",
"E.",
""
],
[
"Verkindt",
"D.",
""
],
[
"Yvert",
"M.",
""
]
] |
In the search for binary systems inspiral signal in interferometric gravitational waves detectors, one needs the generation and placement of a grid of templates. We present an original technique for the placement in the associated parameter space, that makes use of the variation of size of the isomatch ellipses in order to reduce the number of templates necessary to cover the parameter space. This technique avoids the potentially expensive computation of the metric at every point, at the cost of having a small number of ``holes'' in the coverage, representing a few percent of the surface of the parameter space, where the match is slightly lower than specified. A study of the covering efficiency, as well as a comparison with a very simple regular tiling using a single ellipse is made. Simulations show an improvement varying between 6% and 30% for the computing cost in this comparison.
|
0802.2914
|
Kjell Rosquist
|
Kjell Rosquist
|
Some Consequences of Gravitationally Induced Electromagnetic Effects in
Microphysics
|
Write-up of contribution to the 10th Italian-Korean Symposium on
Relativistic Astrophysics held in June 2007
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We discuss the relation between the gravitational and electromagnetic fields
as governed by the Einstein-Maxwell field equations. It is emphasized that the
tendency of the gravitational field to induce electromagnetic effects increases
as the size of the system goes down. In particular, the gravitational field,
according to general relativity, tends to become dominated by the spin at
distances of the order of the Compton wavelength. The relevant quantity which
governs this behavior is the ratio S/M^2 where S is the (spin) angular
momentum. For an electron, S/M^2 ~ 10^44. Therefore, gravitomagnetic effects
will play a significant role in the subatomic domain. To analyze this situation
we use the asymptotic structure in the form of the multipole fields. Some
important consequences for the electromagnetic fields of charged particles with
spin are pointed out. In particular, the gravitational field may induce
corrections to the Coulomb field which can be tested experimentally.
|
[
{
"created": "Wed, 20 Feb 2008 18:05:07 GMT",
"version": "v1"
},
{
"created": "Wed, 20 Feb 2008 21:30:05 GMT",
"version": "v2"
}
] |
2008-02-21
|
[
[
"Rosquist",
"Kjell",
""
]
] |
We discuss the relation between the gravitational and electromagnetic fields as governed by the Einstein-Maxwell field equations. It is emphasized that the tendency of the gravitational field to induce electromagnetic effects increases as the size of the system goes down. In particular, the gravitational field, according to general relativity, tends to become dominated by the spin at distances of the order of the Compton wavelength. The relevant quantity which governs this behavior is the ratio S/M^2 where S is the (spin) angular momentum. For an electron, S/M^2 ~ 10^44. Therefore, gravitomagnetic effects will play a significant role in the subatomic domain. To analyze this situation we use the asymptotic structure in the form of the multipole fields. Some important consequences for the electromagnetic fields of charged particles with spin are pointed out. In particular, the gravitational field may induce corrections to the Coulomb field which can be tested experimentally.
|
2309.11536
|
Bruno Arderucio Costa
|
Bruno Arderucio Costa and Yuri Bonder
|
Signature of Einstein-Cartan theory
| null |
Phys. Lett. B 849 (2024) 138431
|
10.1016/j.physletb.2023.138431
| null |
gr-qc hep-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the physical effects of torsion as predicted by the Einstein-Cartan
theory in the test particle approximation and the non-relativist limit. We
first present the corresponding non-relativistic Hamiltonian for a 2-spinor.
Then, we solve an idealized reflection and transmission problem for a
non-relativistic spin-$\frac{1}{2}$ beam travelling across a spin-polarized
target. We identify deviations in the spin polarizations of the reflected and
transmitted as observables capable of distinguishing Einstein-Cartan from
standard general relativity. If measured, this effect would constitute
compelling evidence for the presence of spacetime torsion.
|
[
{
"created": "Wed, 20 Sep 2023 17:38:23 GMT",
"version": "v1"
},
{
"created": "Tue, 12 Dec 2023 17:39:16 GMT",
"version": "v2"
}
] |
2024-01-05
|
[
[
"Costa",
"Bruno Arderucio",
""
],
[
"Bonder",
"Yuri",
""
]
] |
We study the physical effects of torsion as predicted by the Einstein-Cartan theory in the test particle approximation and the non-relativist limit. We first present the corresponding non-relativistic Hamiltonian for a 2-spinor. Then, we solve an idealized reflection and transmission problem for a non-relativistic spin-$\frac{1}{2}$ beam travelling across a spin-polarized target. We identify deviations in the spin polarizations of the reflected and transmitted as observables capable of distinguishing Einstein-Cartan from standard general relativity. If measured, this effect would constitute compelling evidence for the presence of spacetime torsion.
|
gr-qc/0702013
|
Stefan Haesen
|
Stefan Haesen, Francisco Palomo and Alfonso Romero
|
A new method to construct spacetimes with a spacelike circle action
|
18 pages
| null | null | null |
gr-qc
| null |
A new general procedure to construct realistic spacetimes is introduced. It
is based on the null congruence on a time-oriented Lorentzian manifold
associated to a certain timelike vector field. As an application, new examples
of stably causal Petrov type D spacetimes which obey the timelike convergence
condition and which admit an isometric spacelike circle action are obtained.
|
[
{
"created": "Fri, 2 Feb 2007 09:10:23 GMT",
"version": "v1"
}
] |
2007-05-23
|
[
[
"Haesen",
"Stefan",
""
],
[
"Palomo",
"Francisco",
""
],
[
"Romero",
"Alfonso",
""
]
] |
A new general procedure to construct realistic spacetimes is introduced. It is based on the null congruence on a time-oriented Lorentzian manifold associated to a certain timelike vector field. As an application, new examples of stably causal Petrov type D spacetimes which obey the timelike convergence condition and which admit an isometric spacelike circle action are obtained.
|
0909.1061
|
Mike Stannett
|
Mike Stannett
|
Modelling Quantum Theoretical Trajectories within Geometric Relativistic
Theories
|
14 pages. Presented at "Mathematics, Physics and Philosophy in the
Interpretations of Relativity Theory" (PIRT), 4-6 Septmber 2009, Budapest,
Hungary
| null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Andreka and her colleagues have described various geometrically inspired
first-order theories of special and general relativity, while Szekely's PhD
dissertation focuses on an intermediate logic of accelerated observers. In this
paper we will attempt to incorporate a model of quantum theoretical
trajectories that can reasonably claim to be physically meaningful into those
theories.
We have recently shown that a model of quantum trajectories, based on
discrete finitary motion, is logically equivalent to Feynman's path-integral
formulation when spacetime is assumed to be Euclidean. In this paper we argue
that relativistic observers are subject to the same quantum illusions as in the
Euclidean case: even though motion is discrete and respects no built-in 'arrow
of time', observers have no choice but to perceive particle trajectories as
continuous paths in spacetime.
Whereas the relativistic theories presuppose continuous paths as part of
their axioms, the illusion of continuity allows us to replace this axiom with a
lower-level quantum-inspired axiom concerning discrete jumps in spacetime. We
investigate the nature of these jumps, and how far they can be tied to the
underlying geometric structure of spacetime. In particular, we consider hops
which preserve features of the underlying number field, and investigate the
extent to which all hops can be restricted to be of this form.
We conclude that hop-based motion can also be regarded as an illusion, one
caused by modelling physics in the 'wrong' number system.
|
[
{
"created": "Sat, 5 Sep 2009 22:51:25 GMT",
"version": "v1"
}
] |
2009-09-08
|
[
[
"Stannett",
"Mike",
""
]
] |
Andreka and her colleagues have described various geometrically inspired first-order theories of special and general relativity, while Szekely's PhD dissertation focuses on an intermediate logic of accelerated observers. In this paper we will attempt to incorporate a model of quantum theoretical trajectories that can reasonably claim to be physically meaningful into those theories. We have recently shown that a model of quantum trajectories, based on discrete finitary motion, is logically equivalent to Feynman's path-integral formulation when spacetime is assumed to be Euclidean. In this paper we argue that relativistic observers are subject to the same quantum illusions as in the Euclidean case: even though motion is discrete and respects no built-in 'arrow of time', observers have no choice but to perceive particle trajectories as continuous paths in spacetime. Whereas the relativistic theories presuppose continuous paths as part of their axioms, the illusion of continuity allows us to replace this axiom with a lower-level quantum-inspired axiom concerning discrete jumps in spacetime. We investigate the nature of these jumps, and how far they can be tied to the underlying geometric structure of spacetime. In particular, we consider hops which preserve features of the underlying number field, and investigate the extent to which all hops can be restricted to be of this form. We conclude that hop-based motion can also be regarded as an illusion, one caused by modelling physics in the 'wrong' number system.
|
gr-qc/0307016
|
Israel Quiros
|
Olga Arias, Tame Gonzalez, Yoelsy Leyva and Israel Quiros
|
Exact Scaling Solutions in Normal and Brans-Dicke Models of Dark Energy
|
17 pages, 5 eps figures. This is a published version that comprises
(and extends) the material in papers gr-qc/0212006 and gr-qc/0210097
|
Class.Quant.Grav.20:2563-2578,2003
|
10.1088/0264-9381/20/13/308
| null |
gr-qc
| null |
A linear relationship between the Hubble expansion parameter and the time
derivative of the scalar field is explored in order to derive exact
cosmological, attractor-like solutions, both in Einstein's theory and in
Brans-Dicke gravity with two fluids: a background fluid of ordinary matter,
together with a self-interacting scalar field accounting for the dark energy in
the universe. A priori assumptions about the functional form of the
self-interaction potential or about the scale factor behavior are not
necessary. These are obtained as outputs of the assumed relationship between
the Hubble parameter and the time derivative of the scalar field. A parametric
class of scaling quintessence models given by a self-interaction potential of a
peculiar form: a combination of exponentials with dependence on the barotropic
index of the background fluid, arises. Both normal quintessence described by a
self-interacting scalar field minimally coupled to gravity and Brans-Dicke
quintessence given by a non-minimally coupled scalar field are then analyzed
and the relevance of these models for the description of the cosmic evolution
are discussed in some detail. The stability of these solutions is also briefly
commented on.
|
[
{
"created": "Fri, 4 Jul 2003 01:26:11 GMT",
"version": "v1"
}
] |
2010-10-27
|
[
[
"Arias",
"Olga",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"Leyva",
"Yoelsy",
""
],
[
"Quiros",
"Israel",
""
]
] |
A linear relationship between the Hubble expansion parameter and the time derivative of the scalar field is explored in order to derive exact cosmological, attractor-like solutions, both in Einstein's theory and in Brans-Dicke gravity with two fluids: a background fluid of ordinary matter, together with a self-interacting scalar field accounting for the dark energy in the universe. A priori assumptions about the functional form of the self-interaction potential or about the scale factor behavior are not necessary. These are obtained as outputs of the assumed relationship between the Hubble parameter and the time derivative of the scalar field. A parametric class of scaling quintessence models given by a self-interaction potential of a peculiar form: a combination of exponentials with dependence on the barotropic index of the background fluid, arises. Both normal quintessence described by a self-interacting scalar field minimally coupled to gravity and Brans-Dicke quintessence given by a non-minimally coupled scalar field are then analyzed and the relevance of these models for the description of the cosmic evolution are discussed in some detail. The stability of these solutions is also briefly commented on.
|
1104.0140
|
Matteo Lulli Mr
|
F. Cianfrani, M. Lulli, G. Montani
|
Solution of the noncanonicity puzzle in General Relativity: a new
Hamiltonian formulation
|
Accepted for Publication in Physics Letters B. Major revisions in
Canonical Quantization section for operator ordering choice and in the
definition of 'gauged canonicity' for the classical analysis. 19 pages single
column
| null |
10.1016/j.physletb.2012.03.053
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the transformation leading from Arnowitt, Deser, Misner (ADM)
Hamiltonian formulation of General Relativity (GR) to the $\Gamma\Gamma$ metric
Hamiltonian formulation derived from the Lagrangian density which was firstly
proposed by Einstein. We classify this transformation as gauged canonical -
i.e. canonical modulo a gauge transformation. In such a study we introduce a
new Hamiltonian formulation written in ADM variables which differs from the
usual ADM formulation mainly in a boundary term firstly proposed by Dirac.
Performing the canonical quantization procedure we introduce a new functional
phase which contains an explicit dependence on the fields characterizing the
3+1 splitting. Given a specific regularization procedure our new formulation
privileges the symmetric operator ordering in order to: have a consistent
quantization procedure, avoid anomalies in constraints algebra, be equivalent
to the Wheeler-DeWitt (WDW) quantization. Furthermore we show that this result
is consistent with a path-integral approach.
|
[
{
"created": "Fri, 1 Apr 2011 10:56:07 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Sep 2011 09:52:15 GMT",
"version": "v2"
},
{
"created": "Wed, 21 Mar 2012 11:38:36 GMT",
"version": "v3"
}
] |
2015-05-27
|
[
[
"Cianfrani",
"F.",
""
],
[
"Lulli",
"M.",
""
],
[
"Montani",
"G.",
""
]
] |
We study the transformation leading from Arnowitt, Deser, Misner (ADM) Hamiltonian formulation of General Relativity (GR) to the $\Gamma\Gamma$ metric Hamiltonian formulation derived from the Lagrangian density which was firstly proposed by Einstein. We classify this transformation as gauged canonical - i.e. canonical modulo a gauge transformation. In such a study we introduce a new Hamiltonian formulation written in ADM variables which differs from the usual ADM formulation mainly in a boundary term firstly proposed by Dirac. Performing the canonical quantization procedure we introduce a new functional phase which contains an explicit dependence on the fields characterizing the 3+1 splitting. Given a specific regularization procedure our new formulation privileges the symmetric operator ordering in order to: have a consistent quantization procedure, avoid anomalies in constraints algebra, be equivalent to the Wheeler-DeWitt (WDW) quantization. Furthermore we show that this result is consistent with a path-integral approach.
|
0807.3176
|
Felix M. Lev
|
Felix Lev
|
De Sitter Invariance and a Possible Mechanism of Gravity
|
Latex, 113 pages, no figures
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
It is believed that gravity will be explained in the framework of the
existing quantum theory when one succeeds in eliminating divergencies at large
momenta or small distances (although the phenomenon of gravity has been
observed only at nonrelativistic momenta and large distances). We consider a
quantum-mechanical description of systems of two free particles in de Sitter
invariant quantum theory (i.e. the paper contains nothing but the two-body de
Sitter kinematics). In our pure algebraic approach the cosmological constant
problem does not arise. It is shown that a system can be simultaneously
quasiclassical in relative momentum and energy only if the cosmological
constant is not anomalously small. We explicitly construct the relative
distance operator. The corresponding eigenvectors differ from standard ones at
both, large and small momenta. At large momenta they ensure fast convergence of
quasiclassical wave functions. There also exists an anomalously large (but
finite) contribution from small momenta, which is a consequence of the fact
that the cosmological constant is finite. We argue that gravity might be a
manifestation of this contribution.
|
[
{
"created": "Sun, 20 Jul 2008 19:24:38 GMT",
"version": "v1"
}
] |
2008-07-28
|
[
[
"Lev",
"Felix",
""
]
] |
It is believed that gravity will be explained in the framework of the existing quantum theory when one succeeds in eliminating divergencies at large momenta or small distances (although the phenomenon of gravity has been observed only at nonrelativistic momenta and large distances). We consider a quantum-mechanical description of systems of two free particles in de Sitter invariant quantum theory (i.e. the paper contains nothing but the two-body de Sitter kinematics). In our pure algebraic approach the cosmological constant problem does not arise. It is shown that a system can be simultaneously quasiclassical in relative momentum and energy only if the cosmological constant is not anomalously small. We explicitly construct the relative distance operator. The corresponding eigenvectors differ from standard ones at both, large and small momenta. At large momenta they ensure fast convergence of quasiclassical wave functions. There also exists an anomalously large (but finite) contribution from small momenta, which is a consequence of the fact that the cosmological constant is finite. We argue that gravity might be a manifestation of this contribution.
|
1710.07135
|
Alexei Deriglazov A
|
Alexei A. Deriglazov and Walberto Guzm\'an Ram\'irez
|
Recent progress on the description of relativistic spin: vector model of
spinning particle and rotating body with gravimagnetic moment in General
Relativity
|
Invited review article for the Journal "Advances in Mathematical
Physics". Based on the recent works: arXiv:1312.6247, arXiv:1406.6715,
arXiv:1409.4756, arXiv:1509.05357, arXiv:1511.00645, arXiv:1609.00043. 61
pages, 3 figures
|
Advances in Mathematical Physics, Volume 2017 (2017), Article ID
7397159, 49 pages
|
10.1155/2017/7397159
| null |
gr-qc astro-ph.SR hep-th math-ph math.MP quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We review the recent results on development of vector models of spin and
apply them to study the influence of spin-field interaction on the trajectory
and precession of a spinning particle in external gravitational and
electromagnetic fields. The formalism is developed starting from the Lagrangian
variational problem, which implies both equations of motion and constraints
which should be presented in a model of spinning particle. We present a
detailed analysis of the resulting theory and show that it has reasonable
properties on both classical and quantum level. We describe a number of
applications and show how the vector model clarifies some issues presented in
theoretical description of a relativistic spin: A) One-particle relativistic
quantum mechanics with positive energies and its relation with the Dirac
equation and with relativistic {\it Zitterbewegung}; B) Spin-induced non
commutativity and the problem of covariant formalism; C) Three-dimensional
acceleration consistent with coordinate-independence of the speed of light in
general relativity and rainbow geometry seen by spinning particle; D)
Paradoxical behavior of the Mathisson-Papapetrou-Tulczyjew-Dixon equations of a
rotating body in ultra relativistic limit, and equations with improved
behavior.
|
[
{
"created": "Thu, 19 Oct 2017 13:32:20 GMT",
"version": "v1"
}
] |
2017-10-23
|
[
[
"Deriglazov",
"Alexei A.",
""
],
[
"Ramírez",
"Walberto Guzmán",
""
]
] |
We review the recent results on development of vector models of spin and apply them to study the influence of spin-field interaction on the trajectory and precession of a spinning particle in external gravitational and electromagnetic fields. The formalism is developed starting from the Lagrangian variational problem, which implies both equations of motion and constraints which should be presented in a model of spinning particle. We present a detailed analysis of the resulting theory and show that it has reasonable properties on both classical and quantum level. We describe a number of applications and show how the vector model clarifies some issues presented in theoretical description of a relativistic spin: A) One-particle relativistic quantum mechanics with positive energies and its relation with the Dirac equation and with relativistic {\it Zitterbewegung}; B) Spin-induced non commutativity and the problem of covariant formalism; C) Three-dimensional acceleration consistent with coordinate-independence of the speed of light in general relativity and rainbow geometry seen by spinning particle; D) Paradoxical behavior of the Mathisson-Papapetrou-Tulczyjew-Dixon equations of a rotating body in ultra relativistic limit, and equations with improved behavior.
|
1903.01488
|
Jorge Delgado B.S.
|
Jorge F. M. Delgado, Carlos A. R. Herdeiro, Eugen Radu
|
Kerr black holes with synchronised scalar hair and higher azimuthal
harmonic index
|
13 pages, 13 figures
| null |
10.1016/j.physletb.2019.04.009
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Kerr black holes with synchronised scalar hair and azimuthal harmonic index
$m>1$ are constructed and studied. The corresponding domain of existence has a
broader frequency range than the fundamental $m=1$ family; moreover, larger ADM
masses, $M$ and angular momenta $J$ are allowed. Amongst other salient
features, non-uniqueness of solutions for fixed global quantities is observed:
solutions with the same $M$ and $J$ co-exist, for consecutive values of $m$,
and the ones with larger $m$ are always entropically favoured. Our analysis
demonstrates, moreover, the qualitative universality of various features
observed for $m=1$ solutions, such as the shape of the domain of existence, the
typology of ergo-regions, and the horizon geometry, which is studied through
its isometric embedding in Euclidean 3-space.
|
[
{
"created": "Mon, 4 Mar 2019 19:05:00 GMT",
"version": "v1"
}
] |
2019-04-10
|
[
[
"Delgado",
"Jorge F. M.",
""
],
[
"Herdeiro",
"Carlos A. R.",
""
],
[
"Radu",
"Eugen",
""
]
] |
Kerr black holes with synchronised scalar hair and azimuthal harmonic index $m>1$ are constructed and studied. The corresponding domain of existence has a broader frequency range than the fundamental $m=1$ family; moreover, larger ADM masses, $M$ and angular momenta $J$ are allowed. Amongst other salient features, non-uniqueness of solutions for fixed global quantities is observed: solutions with the same $M$ and $J$ co-exist, for consecutive values of $m$, and the ones with larger $m$ are always entropically favoured. Our analysis demonstrates, moreover, the qualitative universality of various features observed for $m=1$ solutions, such as the shape of the domain of existence, the typology of ergo-regions, and the horizon geometry, which is studied through its isometric embedding in Euclidean 3-space.
|
1505.01310
|
Vladimir Belinski
|
Vladimir A. Belinski
|
On the Supergravitational Solitons
| null | null | null | null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
The extention of the integrable ansatz of pure Einstein gravity to
supergravity is completed. The procedure of construction the exact
supergravitational solitonic solutions is described.
|
[
{
"created": "Wed, 6 May 2015 10:32:05 GMT",
"version": "v1"
}
] |
2015-05-07
|
[
[
"Belinski",
"Vladimir A.",
""
]
] |
The extention of the integrable ansatz of pure Einstein gravity to supergravity is completed. The procedure of construction the exact supergravitational solitonic solutions is described.
|
gr-qc/0602049
|
Alcides Garat
|
Alcides Garat
|
Tetrads in Yang-Mills geometrodynamics
|
This new version has a new abstract and the introduction has been
modified. There is also a new section, applications. This new section has two
subsections: Gauge invariants and Diagonalization of the stress-energy
tensor. The conclusion section has also been substantially modified. There is
a new appendix
|
Grav.Cosmol. 20 (2014) no.2, 116-126
|
10.1134/S0202289314020054
| null |
gr-qc hep-th math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
A new set of tetrads is introduced within the framework of SU(2) X U(1)
Yang-Mills field theories in four dimensional Lorentz curved spacetimes. Each
one of these tetrads diagonalizes separately and explicitly each term of the
Yang-Mills stress-energy tensor. Therefore, three pairs of planes also known as
blades, can be defined, and make up the underlying geometrical structure, at
each point. These tetrad vectors are gauge dependent on one hand, and also in
their definition, there is an additional inherent freedom in the choice of two
vector fields. In order to get rid of the gauge dependence, another set of
tetrads is defined, such that the only choice we have to make is for the two
vector fields. A particular choice is made for these two vector fields such
that they are gauge dependent, but the transformation properties of these
tetrads are analogous to those already known for curved spacetimes where only
electromagnetic fields are present. This analogy allows to establish group
isomorphisms between the local gauge group SU(2), and the tensor product of the
groups of local Lorentz tetrad transformations, either on blade one or blade
two. These theorems show explicitly that the local internal groups of
transformations are isomorphic to local spacetime groups of transformations. As
an example of application of these new tetrads, we exhibit three new gauge
invariant objects, and using these objects we show how to diagonalize the
Yang-Mills stress-energy tensor in a gauge invariant way.
|
[
{
"created": "Mon, 13 Feb 2006 20:12:42 GMT",
"version": "v1"
},
{
"created": "Tue, 26 Jun 2012 13:06:19 GMT",
"version": "v2"
}
] |
2019-08-22
|
[
[
"Garat",
"Alcides",
""
]
] |
A new set of tetrads is introduced within the framework of SU(2) X U(1) Yang-Mills field theories in four dimensional Lorentz curved spacetimes. Each one of these tetrads diagonalizes separately and explicitly each term of the Yang-Mills stress-energy tensor. Therefore, three pairs of planes also known as blades, can be defined, and make up the underlying geometrical structure, at each point. These tetrad vectors are gauge dependent on one hand, and also in their definition, there is an additional inherent freedom in the choice of two vector fields. In order to get rid of the gauge dependence, another set of tetrads is defined, such that the only choice we have to make is for the two vector fields. A particular choice is made for these two vector fields such that they are gauge dependent, but the transformation properties of these tetrads are analogous to those already known for curved spacetimes where only electromagnetic fields are present. This analogy allows to establish group isomorphisms between the local gauge group SU(2), and the tensor product of the groups of local Lorentz tetrad transformations, either on blade one or blade two. These theorems show explicitly that the local internal groups of transformations are isomorphic to local spacetime groups of transformations. As an example of application of these new tetrads, we exhibit three new gauge invariant objects, and using these objects we show how to diagonalize the Yang-Mills stress-energy tensor in a gauge invariant way.
|
2203.09976
|
Lissa de Souza Campos
|
Lissa de Souza Campos
|
Probing thermal effects on static spacetimes with Unruh-DeWitt detectors
|
PhD thesis submitted to the Graduate School of Physics at the
University of Pavia
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In the lack of a full-fledged theory of quantum gravity, I consider free,
scalar, quantum fields on curved spacetimes to gain insight into the
interaction between quantum and gravitational phenomena. I employ the
Unruh-DeWitt detector approach to probe thermal, quantum effects on static,
non-globally hyperbolic spacetimes. In this context, all physical observables
depend on the choice of a boundary condition that cannot be singled-out, in
general, without resorting to an experiment. Notwithstanding, the framework
applied admits a large family of (Robin) boundary conditions and grants us
physically-sensible dynamics and two-point functions of local Hadamard form. I
discover that the anti-Unruh/Hawking effects are not manifest for thermal
states on the BTZ black hole, nor on massless topological black holes of four
dimensions. Whilst the physical significance of these statistical effects
remains puzzling, my work corroborates their non-trivial relation with the KMS
condition and reveals the pivotal influence of the spacetime dimension in their
manifestation. On global monopoles, I find that for massless minimally coupled
fields the transition rate, the thermal fluctuations and the energy density
remain finite at the singularity only for Dirichlet boundary condition. For
conformally coupled fields, although the energy density diverges for all
boundary conditions, the transition rate and the thermal fluctuations vanish at
the monopole; indicating that even if there is infinite energy, no spontaneous
emission occur if the quantum field is not fluctuating. Moreover, I explicitly
construct two-point functions for ground and thermal states on Lifshitz
topological black holes, setting the ground for future explorations in this
Lorentz breaking context.
|
[
{
"created": "Fri, 18 Mar 2022 14:09:37 GMT",
"version": "v1"
}
] |
2022-03-21
|
[
[
"Campos",
"Lissa de Souza",
""
]
] |
In the lack of a full-fledged theory of quantum gravity, I consider free, scalar, quantum fields on curved spacetimes to gain insight into the interaction between quantum and gravitational phenomena. I employ the Unruh-DeWitt detector approach to probe thermal, quantum effects on static, non-globally hyperbolic spacetimes. In this context, all physical observables depend on the choice of a boundary condition that cannot be singled-out, in general, without resorting to an experiment. Notwithstanding, the framework applied admits a large family of (Robin) boundary conditions and grants us physically-sensible dynamics and two-point functions of local Hadamard form. I discover that the anti-Unruh/Hawking effects are not manifest for thermal states on the BTZ black hole, nor on massless topological black holes of four dimensions. Whilst the physical significance of these statistical effects remains puzzling, my work corroborates their non-trivial relation with the KMS condition and reveals the pivotal influence of the spacetime dimension in their manifestation. On global monopoles, I find that for massless minimally coupled fields the transition rate, the thermal fluctuations and the energy density remain finite at the singularity only for Dirichlet boundary condition. For conformally coupled fields, although the energy density diverges for all boundary conditions, the transition rate and the thermal fluctuations vanish at the monopole; indicating that even if there is infinite energy, no spontaneous emission occur if the quantum field is not fluctuating. Moreover, I explicitly construct two-point functions for ground and thermal states on Lifshitz topological black holes, setting the ground for future explorations in this Lorentz breaking context.
|
1409.0105
|
Flavio Mercati
|
Flavio Mercati
|
A Shape Dynamics Tutorial
|
v2.0 (greatly extended and updated), 133 pages, two columns in
landscape format, for optimal reading on a computer screen or on a
short-sided binding printout
| null | null | null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Shape Dynamics (SD) is a new theory of gravity that is based on fewer and
more fundamental first principles than General Relativity (GR). The most
important feature of SD is the replacement of GR's relativity of simultaneity
with a more tractable gauge symmetry, namely invariance under spatial conformal
transformations. This Tutorial contains both a quick introduction for readers
curious about SD and a detailed walk-through of the historical and conceptual
motivations for the theory, its logical development from first principles and
an in-depth description of its present status. The Tutorial is sufficiently
self-contained for an undergrad student with some basic background in GR and
Lagrangian/Hamiltonian mechanics. It is intended both as a reference text for
students approaching the subject and as a review for researchers interested in
the theory.
|
[
{
"created": "Sat, 30 Aug 2014 11:58:29 GMT",
"version": "v1"
},
{
"created": "Mon, 29 May 2017 08:33:38 GMT",
"version": "v2"
}
] |
2017-05-30
|
[
[
"Mercati",
"Flavio",
""
]
] |
Shape Dynamics (SD) is a new theory of gravity that is based on fewer and more fundamental first principles than General Relativity (GR). The most important feature of SD is the replacement of GR's relativity of simultaneity with a more tractable gauge symmetry, namely invariance under spatial conformal transformations. This Tutorial contains both a quick introduction for readers curious about SD and a detailed walk-through of the historical and conceptual motivations for the theory, its logical development from first principles and an in-depth description of its present status. The Tutorial is sufficiently self-contained for an undergrad student with some basic background in GR and Lagrangian/Hamiltonian mechanics. It is intended both as a reference text for students approaching the subject and as a review for researchers interested in the theory.
|
1809.03436
|
Lu\'is Pedro Moura Pena Pires
|
Luis Pires
|
The initial value formulation of the $\lambda$-R model
|
29 pages, 6 figures
| null |
10.1063/5.0027346
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We apply the conformal method to solve the initial value formulation of
general relativity to the $\lambda$-R model, a minimal, anisotropic
modification of general relativity with a preferred foliation and two local
degrees of freedom. We obtain a generalised Lichnerowicz-York equation for the
conformal factor of the metric and derive its properties. We show that the
behaviour of the equation depends on the value of the coupling $\lambda$. In
the absence of a cosmological constant, we recover the existence and uniqueness
properties of the original equation when $\lambda>1/3$ and the trace of the
momentum of the metric, $\pi$, is non-vanishing. For $\pi=0$, we recover the
original Lichnerowicz equation regardless of the value of $\lambda$ and must
therefore restrict the metric to the positive Yamabe class. The same
restriction holds for $\lambda<1/3$, a case in which we show that the spatial
Ricci scalar must also be large enough to guarantee the existence of at least
one solution. Taking the equations of motion into account, this allows us to
prove that there is in general no way of matching both constraint solving data
and time evolution of phase space variables between the $\lambda$-R model and
general relativity, thereby proving the the non-equivalence between the
theories outside of the previously known cases $\lambda=1$ and $\pi=0$.
|
[
{
"created": "Mon, 10 Sep 2018 16:25:18 GMT",
"version": "v1"
}
] |
2024-06-19
|
[
[
"Pires",
"Luis",
""
]
] |
We apply the conformal method to solve the initial value formulation of general relativity to the $\lambda$-R model, a minimal, anisotropic modification of general relativity with a preferred foliation and two local degrees of freedom. We obtain a generalised Lichnerowicz-York equation for the conformal factor of the metric and derive its properties. We show that the behaviour of the equation depends on the value of the coupling $\lambda$. In the absence of a cosmological constant, we recover the existence and uniqueness properties of the original equation when $\lambda>1/3$ and the trace of the momentum of the metric, $\pi$, is non-vanishing. For $\pi=0$, we recover the original Lichnerowicz equation regardless of the value of $\lambda$ and must therefore restrict the metric to the positive Yamabe class. The same restriction holds for $\lambda<1/3$, a case in which we show that the spatial Ricci scalar must also be large enough to guarantee the existence of at least one solution. Taking the equations of motion into account, this allows us to prove that there is in general no way of matching both constraint solving data and time evolution of phase space variables between the $\lambda$-R model and general relativity, thereby proving the the non-equivalence between the theories outside of the previously known cases $\lambda=1$ and $\pi=0$.
|
gr-qc/0609087
|
Wolfgang Tichy
|
Wolfgang Tichy
|
Black hole evolution with the BSSN system by pseudo-spectral methods
|
10 pages, 9 figures
|
Phys.Rev.D74:084005,2006
|
10.1103/PhysRevD.74.084005
| null |
gr-qc
| null |
We present a new pseudo-spectral code for the simulation of evolution systems
that are second order in space. We test this code by evolving a non-linear
scalar wave equation. These non-linear waves can be stably evolved using very
simple constant or radiative boundary conditions, which we show to be
well-posed in the scalar wave case. The main motivation for this work, however,
is to evolve black holes for the first time with the BSSN system by means of a
spectral method. We use our new code to simulate the evolution of a single
black hole using all applicable methods that are usually employed when the BSSN
system is used together with finite differencing methods. In particular, we use
black hole excision and test standard radiative and also constant outer
boundary conditions. Furthermore, we study different gauge choices such as
$1+\log$ and constant densitized lapse. We find that these methods in principle
do work also with our spectral method. However, our simulations fail after
about $100M$ due to unstable exponentially growing modes. The reason for this
failure may be that we evolve the black hole on a full grid without imposing
any symmetries. Such full grid instabilities have also been observed when
finite differencing methods are used to evolve excised black holes with the
BSSN system.
|
[
{
"created": "Wed, 20 Sep 2006 19:05:05 GMT",
"version": "v1"
}
] |
2008-11-26
|
[
[
"Tichy",
"Wolfgang",
""
]
] |
We present a new pseudo-spectral code for the simulation of evolution systems that are second order in space. We test this code by evolving a non-linear scalar wave equation. These non-linear waves can be stably evolved using very simple constant or radiative boundary conditions, which we show to be well-posed in the scalar wave case. The main motivation for this work, however, is to evolve black holes for the first time with the BSSN system by means of a spectral method. We use our new code to simulate the evolution of a single black hole using all applicable methods that are usually employed when the BSSN system is used together with finite differencing methods. In particular, we use black hole excision and test standard radiative and also constant outer boundary conditions. Furthermore, we study different gauge choices such as $1+\log$ and constant densitized lapse. We find that these methods in principle do work also with our spectral method. However, our simulations fail after about $100M$ due to unstable exponentially growing modes. The reason for this failure may be that we evolve the black hole on a full grid without imposing any symmetries. Such full grid instabilities have also been observed when finite differencing methods are used to evolve excised black holes with the BSSN system.
|
1305.5378
|
Farhad Darabi
|
F. Darabi
|
Acceleration of the universe in matter dominant era by conformal
symmetry breaking
|
13 pages. Int. J. Theor. Phys, published online (2013)
|
Int. J. Theor. Phys. 53, 881, (2014)
|
10.1007/s10773-013-1877-8
| null |
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We introduce a scenario in which the breakdown of conformal symmetry is
responsible for the acceleration of universe in the matter dominant era. In
this regard, we consider a self interacting scalar field non-minimally coupled
to the Ricci scalar and the trace of energy-momentum tensor. For a traceless
energy-momentum tensor in radiation dominant era, the coupling to matter
vanishes and we are left with a conformal invariant gravitational action of
Deser, where the universe may experience a decelerating phase in agreement with
observations. In matter dominant era, the coupling to matter no longer
vanishes, the conformal symmetry is broken down, and the matter inevitably
becomes pressureless. The corresponding field equations are obtained and it is
shown that the universe may have an accelerating phase in this era, provided
that the value of self interaction coupling constant satisfies an specific
lower bound. Moreover, we provide a reasonable solution to the coincidence
problem.
|
[
{
"created": "Thu, 23 May 2013 11:01:54 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Nov 2013 07:07:32 GMT",
"version": "v2"
}
] |
2014-01-28
|
[
[
"Darabi",
"F.",
""
]
] |
We introduce a scenario in which the breakdown of conformal symmetry is responsible for the acceleration of universe in the matter dominant era. In this regard, we consider a self interacting scalar field non-minimally coupled to the Ricci scalar and the trace of energy-momentum tensor. For a traceless energy-momentum tensor in radiation dominant era, the coupling to matter vanishes and we are left with a conformal invariant gravitational action of Deser, where the universe may experience a decelerating phase in agreement with observations. In matter dominant era, the coupling to matter no longer vanishes, the conformal symmetry is broken down, and the matter inevitably becomes pressureless. The corresponding field equations are obtained and it is shown that the universe may have an accelerating phase in this era, provided that the value of self interaction coupling constant satisfies an specific lower bound. Moreover, we provide a reasonable solution to the coincidence problem.
|
gr-qc/9508045
| null |
N. Nakazawa
|
Lattice Quantum Gravity from Stochastic 3-Geometries
|
Latex 13 pages, some references are added
| null | null |
NBI-HE-95-27
|
gr-qc
| null |
I propose the Langevin equation for 3-geometries in the Ashtekar's formalism
to describe 4D Euclidean quantum gravity, in the sense that the corresponding
Fokker-Planck hamiltonian recovers the hamiltonian in 4D quantum gravity
exactly. The stochastic time corresponds to the Euclidean time in the gauge,
N=1 and $N^i=0$. In this approach, the time evolution in 4D quantum gravity is
understood as a stochastic process where the quantum fluctuation of ` ` triad
\rq\rq is characterized by the curvature at the one unit time step before. The
lattice regularization of 4D quantum gravity is presented in this context.
|
[
{
"created": "Mon, 21 Aug 1995 00:21:14 GMT",
"version": "v1"
},
{
"created": "Mon, 18 Sep 1995 01:44:17 GMT",
"version": "v2"
}
] |
2008-02-03
|
[
[
"Nakazawa",
"N.",
""
]
] |
I propose the Langevin equation for 3-geometries in the Ashtekar's formalism to describe 4D Euclidean quantum gravity, in the sense that the corresponding Fokker-Planck hamiltonian recovers the hamiltonian in 4D quantum gravity exactly. The stochastic time corresponds to the Euclidean time in the gauge, N=1 and $N^i=0$. In this approach, the time evolution in 4D quantum gravity is understood as a stochastic process where the quantum fluctuation of ` ` triad \rq\rq is characterized by the curvature at the one unit time step before. The lattice regularization of 4D quantum gravity is presented in this context.
|
gr-qc/9710135
|
Roy Maartens
|
Roy Maartens, Megan Govender, Sunil Maharaj
|
Inflation driven by causal heat flux
|
Latex 5 pages; to appear Gen. Rel. Grav
|
Gen.Rel.Grav. 31 (1999) 815-819
|
10.1023/A:1026678019497
| null |
gr-qc
| null |
We find a simple inflationary solution in an inhomogeneous spacetime with
heat flux. The heat flux obeys a causal transport equation, and counteracts the
inflationary decrease of energy density. At late times, the heat flux tends to
zero and the fluid approaches the equation of state $p=-\rho$.
|
[
{
"created": "Fri, 31 Oct 1997 09:00:12 GMT",
"version": "v1"
}
] |
2015-06-25
|
[
[
"Maartens",
"Roy",
""
],
[
"Govender",
"Megan",
""
],
[
"Maharaj",
"Sunil",
""
]
] |
We find a simple inflationary solution in an inhomogeneous spacetime with heat flux. The heat flux obeys a causal transport equation, and counteracts the inflationary decrease of energy density. At late times, the heat flux tends to zero and the fluid approaches the equation of state $p=-\rho$.
|
0906.4918
|
Thomas Schucker
|
Thomas Schucker
|
Ashtekar's variables without spin
|
5 pages, unpublished paper from 1988
| null | null |
HD-THEP-88-12
|
gr-qc
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Ashtekar's variables are shown to arise naturally from a 3+1 split of general
relativity in the Einstein-Cartan formulation. Thereby spinors are exorcised.
|
[
{
"created": "Fri, 26 Jun 2009 12:47:25 GMT",
"version": "v1"
}
] |
2009-06-29
|
[
[
"Schucker",
"Thomas",
""
]
] |
Ashtekar's variables are shown to arise naturally from a 3+1 split of general relativity in the Einstein-Cartan formulation. Thereby spinors are exorcised.
|
gr-qc/0012009
|
Stoytcho Yazadjiev
|
Stoytcho S.Yazadjiev (Sofia University)
|
Distorted charged dilaton black holes
|
14 pages, latex; v2 typos corrected, references added
|
Class.Quant.Grav. 18 (2001) 2105-2116
|
10.1088/0264-9381/18/11/308
| null |
gr-qc astro-ph hep-th
| null |
We construct exact static, axisymmetric solutions of Einstein-Maxwell-dilaton
gravity presenting distorted charged dilaton black holes. The thermodynamics of
such distorted black holes is also discussed.
|
[
{
"created": "Sun, 3 Dec 2000 18:50:09 GMT",
"version": "v1"
},
{
"created": "Wed, 30 May 2001 13:58:34 GMT",
"version": "v2"
}
] |
2009-10-31
|
[
[
"Yazadjiev",
"Stoytcho S.",
"",
"Sofia University"
]
] |
We construct exact static, axisymmetric solutions of Einstein-Maxwell-dilaton gravity presenting distorted charged dilaton black holes. The thermodynamics of such distorted black holes is also discussed.
|
gr-qc/0109069
|
Sayan Kar
|
Naresh Dadhich (IUCAA), Sayan Kar (IITKgp), Sailajananda Mukherji
(NBU), Matt Visser (Washington)
|
R=0 spacetimes and self-dual Lorentzian wormholes
|
8 pages, RevTex two column, one figure
|
Phys.Rev.D65:064004,2002
|
10.1103/PhysRevD.65.064004
| null |
gr-qc
| null |
A two-parameter family of spherically symmetric, static Lorentzian wormholes
is obtained as the general solution of the equation $\rho=\rho_t=0$, where
$\rho = T_{ij} u^iu^j$, $\rho_t = (T_{ij} - {1\over2} T g_{ij}) u^iu^j$, and
$u^i u_i =- 1$. This equation characterizes a class of spacetimes which are
``self dual'' (in the sense of electrogravity duality). The class includes the
Schwarzschild black hole, a family of naked singularities, and a disjoint
family of Lorentzian wormholes, all of which have vanishing scalar curvature
(R=0). Properties of these spacetimes are discussed. Using isotropic
coordinates we delineate clearly the domains of parameter space for which
wormholes, nakedly singular spacetimes and the Schwarzschild black hole can be
obtained. A model for the required ``exotic'' stress-energy is discussed, and
the notion of traversability for the wormholes is also examined.
|
[
{
"created": "Wed, 19 Sep 2001 17:00:02 GMT",
"version": "v1"
}
] |
2010-11-19
|
[
[
"Dadhich",
"Naresh",
"",
"IUCAA"
],
[
"Kar",
"Sayan",
"",
"IITKgp"
],
[
"Mukherji",
"Sailajananda",
"",
"NBU"
],
[
"Visser",
"Matt",
"",
"Washington"
]
] |
A two-parameter family of spherically symmetric, static Lorentzian wormholes is obtained as the general solution of the equation $\rho=\rho_t=0$, where $\rho = T_{ij} u^iu^j$, $\rho_t = (T_{ij} - {1\over2} T g_{ij}) u^iu^j$, and $u^i u_i =- 1$. This equation characterizes a class of spacetimes which are ``self dual'' (in the sense of electrogravity duality). The class includes the Schwarzschild black hole, a family of naked singularities, and a disjoint family of Lorentzian wormholes, all of which have vanishing scalar curvature (R=0). Properties of these spacetimes are discussed. Using isotropic coordinates we delineate clearly the domains of parameter space for which wormholes, nakedly singular spacetimes and the Schwarzschild black hole can be obtained. A model for the required ``exotic'' stress-energy is discussed, and the notion of traversability for the wormholes is also examined.
|
gr-qc/0403046
|
Edward Daw
|
E. J. Daw (1 and 2), J. A. Giaime (1), D. Lormand (3), M. Lubinski
(4), J. Zweizig (5) ((1) Louisiana State University, U.S.A. (2) University of
Sheffield, U.K. (3) LIGO Livingston Observatory, U.S.A. (4) LIGO Hanford
Observatory, U.S.A. (5) California Institute of Technology, U.S.A.)
|
Long term study of the seismic environment at LIGO
|
To be published in Classical and Quantum Gravity. 24 pages, 15
figures
|
Class.Quant.Grav. 21 (2004) 2255-2273
|
10.1088/0264-9381/21/9/003
| null |
gr-qc
| null |
The LIGO experiment aims to detect and study gravitational waves using ground
based laser interferometry. A critical factor to the performance of the
interferometers, and a major consideration in the design of possible future
upgrades, is isolation of the interferometer optics from seismic noise. We
present the results of a detailed program of measurements of the seismic
environment surrounding the LIGO interferometers. We describe the experimental
configuration used to collect the data, which was acquired over a 613 day
period. The measurements focused on the frequency range 0.1-10 Hz, in which the
secondary microseismic peak and noise due to human activity in the vicinity of
the detectors was found to be particularly critical to interferometer
performance. We compare the statistical distribution of the data sets from the
two interferometer sites, construct amplitude spectral densities of seismic
noise amplitude fluctuations with periods of up to 3 months, and analyze the
data for any long term trends in the amplitude of seismic noise in this
critical frequency range.
|
[
{
"created": "Thu, 11 Mar 2004 09:31:27 GMT",
"version": "v1"
}
] |
2009-11-10
|
[
[
"Daw",
"E. J.",
"",
"1 and 2"
],
[
"Giaime",
"J. A.",
""
],
[
"Lormand",
"D.",
""
],
[
"Lubinski",
"M.",
""
],
[
"Zweizig",
"J.",
""
]
] |
The LIGO experiment aims to detect and study gravitational waves using ground based laser interferometry. A critical factor to the performance of the interferometers, and a major consideration in the design of possible future upgrades, is isolation of the interferometer optics from seismic noise. We present the results of a detailed program of measurements of the seismic environment surrounding the LIGO interferometers. We describe the experimental configuration used to collect the data, which was acquired over a 613 day period. The measurements focused on the frequency range 0.1-10 Hz, in which the secondary microseismic peak and noise due to human activity in the vicinity of the detectors was found to be particularly critical to interferometer performance. We compare the statistical distribution of the data sets from the two interferometer sites, construct amplitude spectral densities of seismic noise amplitude fluctuations with periods of up to 3 months, and analyze the data for any long term trends in the amplitude of seismic noise in this critical frequency range.
|
0807.1145
|
Roberto A. Sussman
|
Roberto A. Sussman
|
On spatial volume averaging in Lema\^{\i}tre--Tolman--Bondi dust models.
Part I: back reaction, spacial curvature and binding energy
|
This replacement corrects an important error of the previous version.
The paper (part I) now deals only with back--reaction, spatial curvature and
other issues, leaving "effective acceleration" for a follow up article (part
II). No further modifications will be made. 40 pages in IOP LaTeX format
| null | null | null |
gr-qc astro-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We provide a comprehensive analytic study (rigorous and qualitative) of the
conditions for the existence of a a positive kinematic back reaction term
$\QQ>0$, in the context of Buchert's scalar averaging formalism applied to
spherically symmetric Lema\^itre-Tolman-Bondi (LTB) dust solutions in which
averaging domains are given as spherical comoving regions containing a symmetry
center. We introduce proper volume and quasi-local average functionals and
functions in order to examine the conditions for $\QQ\geq 0$, and in the
process we also explore the relation between back reaction, spatial curvature
and binding energy for a wide variety of LTB configurations. The back reaction
term is positive for all "hyperbolic" regular domains with negative spatial
curvature, either in the full radial range or in the radial asymptotic range.
This result is also valid if these domains contain an inner "elliptic" region
with positive curvature undergoing local collapse. For some cases in which
positive spatial curvature decreases asymptotically, the conditions for a
positive back reaction can still be met but seem to be more restrictive. Since
$\QQ>0$ is a necessary condition for a positive "effective" acceleration that
would mimic the effect of dark energy (in the context of Buchert's formalism),
we examine this issue in LTB models in a follow up paper (part II).
|
[
{
"created": "Tue, 8 Jul 2008 00:03:48 GMT",
"version": "v1"
},
{
"created": "Tue, 5 Aug 2008 08:52:23 GMT",
"version": "v2"
},
{
"created": "Sat, 10 Jan 2009 07:14:26 GMT",
"version": "v3"
},
{
"created": "Mon, 21 Dec 2009 02:30:29 GMT",
"version": "v4"
}
] |
2009-12-21
|
[
[
"Sussman",
"Roberto A.",
""
]
] |
We provide a comprehensive analytic study (rigorous and qualitative) of the conditions for the existence of a a positive kinematic back reaction term $\QQ>0$, in the context of Buchert's scalar averaging formalism applied to spherically symmetric Lema\^itre-Tolman-Bondi (LTB) dust solutions in which averaging domains are given as spherical comoving regions containing a symmetry center. We introduce proper volume and quasi-local average functionals and functions in order to examine the conditions for $\QQ\geq 0$, and in the process we also explore the relation between back reaction, spatial curvature and binding energy for a wide variety of LTB configurations. The back reaction term is positive for all "hyperbolic" regular domains with negative spatial curvature, either in the full radial range or in the radial asymptotic range. This result is also valid if these domains contain an inner "elliptic" region with positive curvature undergoing local collapse. For some cases in which positive spatial curvature decreases asymptotically, the conditions for a positive back reaction can still be met but seem to be more restrictive. Since $\QQ>0$ is a necessary condition for a positive "effective" acceleration that would mimic the effect of dark energy (in the context of Buchert's formalism), we examine this issue in LTB models in a follow up paper (part II).
|
2107.00463
|
Mostafa Bousder Mr
|
M. Bousder, K. El Bourakadi and M.Bennai
|
Charged 4D Einstein-Gauss-Bonnet Black Hole: Vacuum solutions, Cauchy
Horizon, Thermodynamics
|
16 pages, 4 figures
|
Physics of the Dark Universe 32C (2021) 100839
|
10.1016/j.dark.2021.100839
| null |
gr-qc astro-ph.HE
|
http://creativecommons.org/licenses/by/4.0/
|
In this paper, we investigate the four-dimensional Einstein-Gauss-Bonnet
black hole. The thermodynamic variables and equations of state of black holes
are obtained in terms of a new parameterization. We discuss a formulation of
the van der Waals equation by studying the effects of the temperature on P-V
isotherms. We show the influence of the Cauchy horizon on the thermodynamic
parameters. We prove by different methods, that the black hole entropy obey
area law (plus logarithmic term that depends on the Gauss-Bonnet coupling
{\alpha}). We propose a physical meaning for the logarithmic correction to the
area law. This work can be extended to the extremal EGB black hole, in that
case, we study the relationship between compressibility factor, specific heat
and the coupling {\alpha}.
|
[
{
"created": "Wed, 30 Jun 2021 10:38:06 GMT",
"version": "v1"
}
] |
2021-07-02
|
[
[
"Bousder",
"M.",
""
],
[
"Bourakadi",
"K. El",
""
],
[
"Bennai",
"M.",
""
]
] |
In this paper, we investigate the four-dimensional Einstein-Gauss-Bonnet black hole. The thermodynamic variables and equations of state of black holes are obtained in terms of a new parameterization. We discuss a formulation of the van der Waals equation by studying the effects of the temperature on P-V isotherms. We show the influence of the Cauchy horizon on the thermodynamic parameters. We prove by different methods, that the black hole entropy obey area law (plus logarithmic term that depends on the Gauss-Bonnet coupling {\alpha}). We propose a physical meaning for the logarithmic correction to the area law. This work can be extended to the extremal EGB black hole, in that case, we study the relationship between compressibility factor, specific heat and the coupling {\alpha}.
|
1509.00232
|
Vardarajan Suneeta
|
Dhanya S. Menon, Vardarajan Suneeta
|
Necessary conditions for an AdS-type instability
|
31 pages, version to appear in Physical Review D
|
Phys. Rev. D 93, 024044 (2016)
|
10.1103/PhysRevD.93.024044
| null |
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this work, we analyze the necessary conditions for a nonlinear AdS-type
instability in the gravity-scalar field system. In particular, we discuss the
necessary conditions for a cascade of energy to higher modes by applying
results in KAM theory. Our analytical framework explains numerical observations
of instability of spacetimes even when the spectrum is only asymptotically
resonant, and the fact that a minimum field amplitude is needed to trigger it.
Our framework can be applied for similar stability analyses of fields in
(locally) asymptotically AdS spacetimes. We illustrate this with the example of
the AdS soliton. Further, we conjecture on the possible reasons for
quasi-periodic behaviour observed in perturbations of AdS spacetime. Certain
properties of the eigenfunctions of the linear system dictate whether there
will be localization in space leading to black hole formation. These properties
are examined using the asymptotics of Jacobi polynomials. Finally we discuss
recent results on the AdS instability in Einstein-Gauss-Bonnet gravity in light
of our work.
|
[
{
"created": "Tue, 1 Sep 2015 11:23:15 GMT",
"version": "v1"
},
{
"created": "Sun, 6 Sep 2015 09:42:36 GMT",
"version": "v2"
},
{
"created": "Mon, 2 Nov 2015 04:42:15 GMT",
"version": "v3"
},
{
"created": "Tue, 29 Dec 2015 06:20:25 GMT",
"version": "v4"
}
] |
2016-02-03
|
[
[
"Menon",
"Dhanya S.",
""
],
[
"Suneeta",
"Vardarajan",
""
]
] |
In this work, we analyze the necessary conditions for a nonlinear AdS-type instability in the gravity-scalar field system. In particular, we discuss the necessary conditions for a cascade of energy to higher modes by applying results in KAM theory. Our analytical framework explains numerical observations of instability of spacetimes even when the spectrum is only asymptotically resonant, and the fact that a minimum field amplitude is needed to trigger it. Our framework can be applied for similar stability analyses of fields in (locally) asymptotically AdS spacetimes. We illustrate this with the example of the AdS soliton. Further, we conjecture on the possible reasons for quasi-periodic behaviour observed in perturbations of AdS spacetime. Certain properties of the eigenfunctions of the linear system dictate whether there will be localization in space leading to black hole formation. These properties are examined using the asymptotics of Jacobi polynomials. Finally we discuss recent results on the AdS instability in Einstein-Gauss-Bonnet gravity in light of our work.
|
1308.0896
|
Yury Eroshenko
|
V.I. Dokuchaev and Yu.N. Eroshenko
|
Non-orientable wormholes as portals to the mirror world
|
7 pages, 1 figure
|
Phys. Rev. D 90, 024056 (2014)
|
10.1103/PhysRevD.90.024056
| null |
gr-qc astro-ph.HE
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We examine the compatibility of the mirror matter concept with the
non-orientable wormholes. If any particle (or classical object) is traversing
through the non-orientable wormhole, it turns into a corresponding mirror
particle and vice versa. The critical sonic point in the hydrodynamical flow of
the perfect fluid is located exactly at the throat of the wormhole. This means
that wormholes are traversable for the fluid. The astrophysical signatures of
the presence of non-orientable wormholes in the Universe are discussed. Some
non-trivial aspects of the non-orientable wormholes electrodynamics are
considered.
|
[
{
"created": "Mon, 5 Aug 2013 07:05:49 GMT",
"version": "v1"
},
{
"created": "Mon, 17 Mar 2014 08:28:24 GMT",
"version": "v2"
},
{
"created": "Fri, 1 Aug 2014 12:32:08 GMT",
"version": "v3"
}
] |
2014-08-04
|
[
[
"Dokuchaev",
"V. I.",
""
],
[
"Eroshenko",
"Yu. N.",
""
]
] |
We examine the compatibility of the mirror matter concept with the non-orientable wormholes. If any particle (or classical object) is traversing through the non-orientable wormhole, it turns into a corresponding mirror particle and vice versa. The critical sonic point in the hydrodynamical flow of the perfect fluid is located exactly at the throat of the wormhole. This means that wormholes are traversable for the fluid. The astrophysical signatures of the presence of non-orientable wormholes in the Universe are discussed. Some non-trivial aspects of the non-orientable wormholes electrodynamics are considered.
|
2402.10459
|
Jin Saito
|
Jin Saito, Zhibang Yao, Tsutomu Kobayashi
|
PPN meets EFT of dark energy: Post-Newtonian approximation in
higher-order scalar-tensor theories
|
18 pages, 2 figures
| null | null |
RUP-24-3
|
gr-qc astro-ph.CO
|
http://creativecommons.org/licenses/by/4.0/
|
We study the post-Newtonian limit of higher-order scalar-tensor theories that
are degenerate in the unitary gauge. They can be conveniently described by the
effective field theory (EFT) of dark energy. We determine all the parametrized
post-Newtonian (PPN) parameters in terms of the EFT of dark energy parameters.
Experimental bounds on the PPN parameters are then translated to constraints on
the EFT parameters. We present a Lagrangian of a unitary degenerate
higher-order scalar-tensor theory characterized by a single function of the
kinetic term of the scalar field whose PPN parameters have the same values as
in general relativity.
|
[
{
"created": "Fri, 16 Feb 2024 05:36:46 GMT",
"version": "v1"
}
] |
2024-02-19
|
[
[
"Saito",
"Jin",
""
],
[
"Yao",
"Zhibang",
""
],
[
"Kobayashi",
"Tsutomu",
""
]
] |
We study the post-Newtonian limit of higher-order scalar-tensor theories that are degenerate in the unitary gauge. They can be conveniently described by the effective field theory (EFT) of dark energy. We determine all the parametrized post-Newtonian (PPN) parameters in terms of the EFT of dark energy parameters. Experimental bounds on the PPN parameters are then translated to constraints on the EFT parameters. We present a Lagrangian of a unitary degenerate higher-order scalar-tensor theory characterized by a single function of the kinetic term of the scalar field whose PPN parameters have the same values as in general relativity.
|
gr-qc/0409069
|
Paola Zizzi
|
Paola A. Zizzi
|
A Minimal Model for Quantum Gravity
|
11 pages, 4 figures, Contributed paper at DICE 2004, 1-4 September
2004, Piombino, Italy minor changes, misprints corrected
|
Mod.Phys.Lett. A20 (2005) 645-653
|
10.1142/S021773230501683X
| null |
gr-qc hep-th quant-ph
| null |
We argue that the model of a quantum computer with N qubits on a quantum
space background, which is a fuzzy sphere with n=2^N elementary cells, can be
viewed as the minimal model for Quantum Gravity. In fact, it is discrete, has
no free parameters, is Lorentz invariant, naturally realizes the Holographic
Principle, and defines a subset of punctures of spin networks' edges of Loop
Quantum Gravity labelled by spins j=2^(N-1)-1/2. In this model, the discrete
area spectrum of the cells, which is not equally spaced, is given in units of
the minimal area of Loop Quantum Gravity (for j=1/2), and provides a discrete
emission spectrum for quantum black holes. When the black hole emits one string
of N bits encoded in one of the n cells, its horizon area decreases of an
amount equal to the area of one cell.
|
[
{
"created": "Sat, 18 Sep 2004 03:45:19 GMT",
"version": "v1"
},
{
"created": "Sat, 29 Jan 2005 18:40:31 GMT",
"version": "v2"
}
] |
2009-11-10
|
[
[
"Zizzi",
"Paola A.",
""
]
] |
We argue that the model of a quantum computer with N qubits on a quantum space background, which is a fuzzy sphere with n=2^N elementary cells, can be viewed as the minimal model for Quantum Gravity. In fact, it is discrete, has no free parameters, is Lorentz invariant, naturally realizes the Holographic Principle, and defines a subset of punctures of spin networks' edges of Loop Quantum Gravity labelled by spins j=2^(N-1)-1/2. In this model, the discrete area spectrum of the cells, which is not equally spaced, is given in units of the minimal area of Loop Quantum Gravity (for j=1/2), and provides a discrete emission spectrum for quantum black holes. When the black hole emits one string of N bits encoded in one of the n cells, its horizon area decreases of an amount equal to the area of one cell.
|
1406.7555
|
Wei Lu
|
Wei Lu
|
Modified Einstein-Cartan Gravity and its Implications for Cosmology
|
11 pages, typos corrected, references added
| null | null | null |
gr-qc astro-ph.CO hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a modification of Einstein-Cartan gravity equations. The modified
cosmology departs from the standard model of cosmology for small Hubble
parameter. A characteristic Hubble scale h0, which is intrinsically related to
cosmological constant, marks the boundary between the validity domains of the
standard model of cosmology and modified cosmology. For large Hubble parameter,
the standard model of cosmology is restored. In the opposite limit of small
Hubble parameter, which is the case for present epoch, Lorentz-violating
effects would manifest themselves. One of the implications is that there may be
no need to invoke dark matter to account for cosmological mass discrepancies.
|
[
{
"created": "Sun, 29 Jun 2014 20:10:41 GMT",
"version": "v1"
},
{
"created": "Thu, 3 Jul 2014 23:22:49 GMT",
"version": "v2"
}
] |
2015-07-21
|
[
[
"Lu",
"Wei",
""
]
] |
We propose a modification of Einstein-Cartan gravity equations. The modified cosmology departs from the standard model of cosmology for small Hubble parameter. A characteristic Hubble scale h0, which is intrinsically related to cosmological constant, marks the boundary between the validity domains of the standard model of cosmology and modified cosmology. For large Hubble parameter, the standard model of cosmology is restored. In the opposite limit of small Hubble parameter, which is the case for present epoch, Lorentz-violating effects would manifest themselves. One of the implications is that there may be no need to invoke dark matter to account for cosmological mass discrepancies.
|
1910.04219
|
Ivica Smoli\'c
|
Ana Bokuli\'c, Ivica Smoli\'c
|
Schwarzschild spacetime immersed in test nonlinear electromagnetic
fields
|
18 pages, 2 figures; slightly revised, published version
|
Class. Quantum Grav. 37 (2020) 055004
|
10.1088/1361-6382/ab6390
|
ZTF-EP-19-03
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Kerr black hole immersed in test, asymptotically homogeneous magnetic field,
aligned along the symmetry axis, is described by Wald's solution. We show how
the static case of this solution may be generalized for nonlinear
electromagnetic models via perturbative approach. Using this technique we find
the lowest order correction to Wald's solution on Schwarzschild spacetime in
Euler--Heisenberg and Born--Infeld theories. Finally, we discuss the problem of
highly conducting star in asymptotically homogeneous magnetic field.
|
[
{
"created": "Wed, 9 Oct 2019 19:45:25 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2020 23:56:39 GMT",
"version": "v2"
}
] |
2020-02-11
|
[
[
"Bokulić",
"Ana",
""
],
[
"Smolić",
"Ivica",
""
]
] |
Kerr black hole immersed in test, asymptotically homogeneous magnetic field, aligned along the symmetry axis, is described by Wald's solution. We show how the static case of this solution may be generalized for nonlinear electromagnetic models via perturbative approach. Using this technique we find the lowest order correction to Wald's solution on Schwarzschild spacetime in Euler--Heisenberg and Born--Infeld theories. Finally, we discuss the problem of highly conducting star in asymptotically homogeneous magnetic field.
|
1307.0482
|
Marcos Brum
|
Marcos Brum and Klaus Fredenhagen
|
"Vacuum-like" Hadamard states for quantum fields on curved spacetimes
|
Accepted for publication in CQG. Added Theorem 3.0.1 proving the
purity of the states, added Theorem A.1 proving the essential
self-adjointness of the elliptic operator. References were also added
| null |
10.1088/0264-9381/31/2/025024
| null |
gr-qc math-ph math.MP
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We present a modification of the recently proposed Sorkin-Johnston states for
scalar free quantum fields on a class of globally hyperbolic spacetimes
possessing compact Cauchy hypersurfaces. The modification relies on a smooth
cutoff of the commutator function and leads always to Hadamard states, in
contrast to the original Sorkin-Johnston states. The modified Sorkin-Johnston
states are, however, due to the smoothing no longer uniquely associated to the
spacetime.
|
[
{
"created": "Mon, 1 Jul 2013 18:58:36 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Nov 2013 16:09:06 GMT",
"version": "v2"
}
] |
2013-12-23
|
[
[
"Brum",
"Marcos",
""
],
[
"Fredenhagen",
"Klaus",
""
]
] |
We present a modification of the recently proposed Sorkin-Johnston states for scalar free quantum fields on a class of globally hyperbolic spacetimes possessing compact Cauchy hypersurfaces. The modification relies on a smooth cutoff of the commutator function and leads always to Hadamard states, in contrast to the original Sorkin-Johnston states. The modified Sorkin-Johnston states are, however, due to the smoothing no longer uniquely associated to the spacetime.
|
1601.06772
|
Igor Nikitin
|
Igor Nikitin
|
Tachyonic models of dark matter
| null | null | null | null |
gr-qc astro-ph.GA
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We consider a spherically symmetric stationary problem in General Relativity,
including a black hole, inflow of normal and tachyonic matter and outflow of
tachyonic matter. Computations in a weak field limit show that the resulting
concentration of matter around the black hole leads to gravitational effects
equivalent to those associated with dark matter halo. In particular, the model
reproduces asymptotically constant galactic rotation curves, if the tachyonic
flows of the central supermassive black hole in the galaxy are considered as a
main contribution.
|
[
{
"created": "Sat, 23 Jan 2016 14:17:24 GMT",
"version": "v1"
}
] |
2016-01-27
|
[
[
"Nikitin",
"Igor",
""
]
] |
We consider a spherically symmetric stationary problem in General Relativity, including a black hole, inflow of normal and tachyonic matter and outflow of tachyonic matter. Computations in a weak field limit show that the resulting concentration of matter around the black hole leads to gravitational effects equivalent to those associated with dark matter halo. In particular, the model reproduces asymptotically constant galactic rotation curves, if the tachyonic flows of the central supermassive black hole in the galaxy are considered as a main contribution.
|
2008.04003
|
Keisuke Nakashi
|
Keisuke Nakashi and Masashi Kimura
|
Towards rotating non-circular black holes in string-inspired gravity
|
23 pages, v2: minor revisions, accepted for publication in Phys. Rev.
D
|
Phys. Rev. D 102, 084021 (2020)
|
10.1103/PhysRevD.102.084021
|
RUP-20-28
|
gr-qc hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study stationary slowly rotating black holes, up to quadratic order in the
spin angular momentum, in dynamical Chern-Simons gravity and shift symmetric
Einstein scalar Gauss-Bonnet gravity, as models of string-inspired gravities.
These gravity theories modify general relativity by introducing dynamical
scalar fields coupled with curvature invariants. We show that the linear time
dependence of the scalar fields is allowed from the stationarity of the
effective stress energy tensors. However, these time dependent scalar fields
yield singular behavior of the metric functions at the black hole horizons, or
they are incompatible with the stationarity of the spacetimes. Thus, these
gravity theories admit only known solutions as regular stationary solutions.
Our results suggest the non-existence of rotating non-circular black holes in
these gravity theories.
|
[
{
"created": "Mon, 10 Aug 2020 10:08:08 GMT",
"version": "v1"
},
{
"created": "Fri, 18 Sep 2020 06:17:42 GMT",
"version": "v2"
}
] |
2020-10-14
|
[
[
"Nakashi",
"Keisuke",
""
],
[
"Kimura",
"Masashi",
""
]
] |
We study stationary slowly rotating black holes, up to quadratic order in the spin angular momentum, in dynamical Chern-Simons gravity and shift symmetric Einstein scalar Gauss-Bonnet gravity, as models of string-inspired gravities. These gravity theories modify general relativity by introducing dynamical scalar fields coupled with curvature invariants. We show that the linear time dependence of the scalar fields is allowed from the stationarity of the effective stress energy tensors. However, these time dependent scalar fields yield singular behavior of the metric functions at the black hole horizons, or they are incompatible with the stationarity of the spacetimes. Thus, these gravity theories admit only known solutions as regular stationary solutions. Our results suggest the non-existence of rotating non-circular black holes in these gravity theories.
|
gr-qc/0003077
| null |
Bahram Mashhoon and Dietmar S. Theiss
|
Relativistic Effects in the Motion of the Moon
|
LaTeX file, no figures, 13 pages, to appear in: 'Testing relativistic
gravity in space', edited by C. Laemmerzahl, C.W.F. Everitt and F.W. Hehl
(Springer, Berlin 2000)
|
Lect.Notes Phys. 562 (2001) 310-316
|
10.1007/3-540-40988-2_15
| null |
gr-qc
| null |
The main general relativistic effects in the motion of the Moon are briefly
reviewed. The possibility of detection of the solar gravitomagnetic
contributions to the mean motions of the lunar node and perigee is discussed.
|
[
{
"created": "Mon, 20 Mar 2000 05:22:09 GMT",
"version": "v1"
},
{
"created": "Wed, 22 Mar 2000 00:17:53 GMT",
"version": "v2"
}
] |
2016-12-07
|
[
[
"Mashhoon",
"Bahram",
""
],
[
"Theiss",
"Dietmar S.",
""
]
] |
The main general relativistic effects in the motion of the Moon are briefly reviewed. The possibility of detection of the solar gravitomagnetic contributions to the mean motions of the lunar node and perigee is discussed.
|
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